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 $194.86   11.550%   $217.3663   $217.37   $217.35   $217.40  
  Purchase #2 $25.87   9.488%   $28.3245   $28.32   $28.30   $28.30  
  Purchase #3 $47.81   5.424%   $50.4032   $50.40   $50.40   $50.40  
  Purchase #4 $70.32   7.508%   $75.5996   $75.60   $75.60   $75.60  
  Purchase #5 $98.97   5.747%   $104.6578   $104.66   $104.65   $104.70  
  Purchase #6 $203.30   10.770%   $225.1954   $225.20   $225.20   $225.20  
  Purchase #7 $237.45   8.161%   $256.8283   $256.83   $256.85   $256.80  
  7 purchase totals = $878.58       $958.3751   $958.38   $958.35   $958.40