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 $222.77   5.721%   $235.5147   $235.51   $235.50   $235.50  
  Purchase #2 $46.96   5.753%   $49.6616   $49.66   $49.65   $49.70  
  Purchase #3 $31.95   9.224%   $34.8971   $34.90   $34.90   $34.90  
  Purchase #4 $175.30   4.501%   $183.1903   $183.19   $183.20   $183.20  
  Purchase #5 $167.69   4.521%   $175.2713   $175.27   $175.25   $175.30  
  Purchase #6 $247.33   6.425%   $263.221   $263.22   $263.20   $263.20  
  Purchase #7 $64.78   13.577%   $73.5752   $73.58   $73.60   $73.60  
  7 purchase totals = $956.78       $1,015.3312   $1,015.33   $1,015.30   $1,015.40