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 $202.29   11.726%   $226.0105   $226.01   $226.00   $226.00  
  Purchase #2 $223.80   5.123%   $235.2653   $235.27   $235.25   $235.30  
  Purchase #3 $243.77   8.183%   $263.7177   $263.72   $263.70   $263.70  
  Purchase #4 $142.76   9.655%   $156.5435   $156.54   $156.55   $156.50  
  Purchase #5 $186.62   4.426%   $194.8798   $194.88   $194.90   $194.90  
  Purchase #6 $149.47   12.122%   $167.5888   $167.59   $167.60   $167.60  
  Purchase #7 $193.97   8.608%   $210.6669   $210.67   $210.65   $210.70  
  7 purchase totals = $1,342.68       $1,454.6725   $1,454.68   $1,454.65   $1,454.70