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 $202.93   7.161%   $217.4618   $217.46   $217.45   $217.50  
  Purchase #2 $16.63   12.140%   $18.6489   $18.65   $18.65   $18.60  
  Purchase #3 $143.62   6.667%   $153.1951   $153.20   $153.20   $153.20  
  Purchase #4 $92.27   5.598%   $97.4353   $97.44   $97.45   $97.40  
  Purchase #5 $114.72   5.349%   $120.8564   $120.86   $120.85   $120.90  
  Purchase #6 $96.57   6.316%   $102.6694   $102.67   $102.65   $102.70  
  Purchase #7 $46.85   10.371%   $51.7088   $51.71   $51.70   $51.70  
  7 purchase totals = $713.59       $761.9757   $761.99   $761.95   $762.00