Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $208.98   12.783%   $235.6939   $235.69   $235.70   $235.70  
  Purchase #2 $226.68   3.809%   $235.3142   $235.31   $235.30   $235.30  
  Purchase #3 $150.38   11.697%   $167.9699   $167.97   $167.95   $168.00  
  Purchase #4 $168.54   11.600%   $188.0906   $188.09   $188.10   $188.10  
  Purchase #5 $111.60   11.463%   $124.3927   $124.39   $124.40   $124.40  
  Purchase #6 $166.86   6.788%   $178.1865   $178.19   $178.20   $178.20  
  Purchase #7 $239.58   10.359%   $264.3981   $264.40   $264.40   $264.40  
  7 purchase totals = $1,272.62       $1,394.0459   $1,394.04   $1,394.05   $1,394.10