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 $181.71   10.628%   $201.0221   $201.02   $201.00   $201.00  
  Purchase #2 $33.55   4.533%   $35.0708   $35.07   $35.05   $35.10  
  Purchase #3 $44.97   11.645%   $50.2068   $50.21   $50.20   $50.20  
  Purchase #4 $71.58   6.244%   $76.0495   $76.05   $76.05   $76.00  
  Purchase #5 $159.69   9.298%   $174.538   $174.54   $174.55   $174.50  
  Purchase #6 $240.83   5.197%   $253.3459   $253.35   $253.35   $253.30  
  Purchase #7 $61.87   4.415%   $64.6016   $64.60   $64.60   $64.60  
  7 purchase totals = $794.20       $854.8347   $854.84   $854.80   $854.70