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 $62.97   10.464%   $69.5592   $69.56   $69.55   $69.60  
  Purchase #2 $195.86   8.187%   $211.8951   $211.90   $211.90   $211.90  
  Purchase #3 $24.80   4.719%   $25.9703   $25.97   $25.95   $26.00  
  Purchase #4 $169.93   8.198%   $183.8609   $183.86   $183.85   $183.90  
  Purchase #5 $85.95   13.698%   $97.7234   $97.72   $97.70   $97.70  
  Purchase #6 $95.93   6.515%   $102.1798   $102.18   $102.20   $102.20  
  Purchase #7 $40.31   11.836%   $45.0811   $45.08   $45.10   $45.10  
  7 purchase totals = $675.75       $736.2698   $736.27   $736.25   $736.40