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 $211.48   12.465%   $237.841   $237.84   $237.85   $237.80  
  Purchase #2 $57.70   4.595%   $60.3513   $60.35   $60.35   $60.40  
  Purchase #3 $148.38   8.828%   $161.479   $161.48   $161.50   $161.50  
  Purchase #4 $89.71   4.103%   $93.3908   $93.39   $93.40   $93.40  
  Purchase #5 $89.78   8.576%   $97.4795   $97.48   $97.50   $97.50  
  Purchase #6 $46.66   3.815%   $48.4401   $48.44   $48.45   $48.40  
  Purchase #7 $55.85   13.115%   $63.1747   $63.17   $63.15   $63.20  
  7 purchase totals = $699.56       $762.1564   $762.15   $762.20   $762.20