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 $186.62   4.558%   $195.1261   $195.13   $195.15   $195.10  
  Purchase #2 $133.67   8.179%   $144.6029   $144.60   $144.60   $144.60  
  Purchase #3 $59.25   6.733%   $63.2393   $63.24   $63.25   $63.20  
  Purchase #4 $231.72   13.290%   $262.5156   $262.52   $262.50   $262.50  
  Purchase #5 $154.92   4.635%   $162.1005   $162.10   $162.10   $162.10  
  Purchase #6 $96.33   8.872%   $104.8764   $104.88   $104.90   $104.90  
  Purchase #7 $28.37   6.268%   $30.1482   $30.15   $30.15   $30.10  
  7 purchase totals = $890.88       $962.6090   $962.62   $962.65   $962.50