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 $62.95   8.424%   $68.2529   $68.25   $68.25   $68.30  
  Purchase #2 $33.34   10.276%   $36.766   $36.77   $36.75   $36.80  
  Purchase #3 $92.67   7.150%   $99.2959   $99.30   $99.30   $99.30  
  Purchase #4 $207.69   9.299%   $227.0031   $227.00   $227.00   $227.00  
  Purchase #5 $217.38   6.495%   $231.4988   $231.50   $231.50   $231.50  
  Purchase #6 $68.80   5.562%   $72.6267   $72.63   $72.65   $72.60  
  Purchase #7 $111.59   13.140%   $126.2529   $126.25   $126.25   $126.30  
  7 purchase totals = $794.42       $861.6963   $861.70   $861.70   $861.80