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 $62.40   7.315%   $66.9646   $66.96   $66.95   $67.00  
  Purchase #2 $32.94   4.785%   $34.5162   $34.52   $34.50   $34.50  
  Purchase #3 $187.95   3.243%   $194.0452   $194.05   $194.05   $194.00  
  Purchase #4 $132.62   13.680%   $150.7624   $150.76   $150.75   $150.80  
  Purchase #5 $54.88   5.810%   $58.0685   $58.07   $58.05   $58.10  
  Purchase #6 $50.51   9.334%   $55.2246   $55.22   $55.20   $55.20  
  Purchase #7 $180.87   11.450%   $201.5796   $201.58   $201.60   $201.60  
  7 purchase totals = $702.17       $761.1611   $761.16   $761.10   $761.20