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 $83.86   12.760%   $94.5605   $94.56   $94.55   $94.60  
  Purchase #2 $96.66   11.698%   $107.9673   $107.97   $107.95   $108.00  
  Purchase #3 $35.32   3.138%   $36.4283   $36.43   $36.45   $36.40  
  Purchase #4 $103.82   8.156%   $112.2876   $112.29   $112.30   $112.30  
  Purchase #5 $111.27   5.335%   $117.2063   $117.21   $117.20   $117.20  
  Purchase #6 $67.86   5.234%   $71.4118   $71.41   $71.40   $71.40  
  Purchase #7 $199.60   3.768%   $207.1209   $207.12   $207.10   $207.10  
  7 purchase totals = $698.39       $746.9827   $746.99   $746.95   $747.00