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 $85.94   11.622%   $95.9279   $95.93   $95.95   $95.90  
  Purchase #2 $57.87   12.728%   $65.2357   $65.24   $65.25   $65.20  
  Purchase #3 $111.85   6.140%   $118.7176   $118.72   $118.70   $118.70  
  Purchase #4 $107.58   13.804%   $122.4303   $122.43   $122.45   $122.40  
  Purchase #5 $99.82   12.636%   $112.4333   $112.43   $112.45   $112.40  
  Purchase #6 $117.95   6.680%   $125.8291   $125.83   $125.85   $125.80  
  Purchase #7 $190.45   10.794%   $211.0072   $211.01   $211.00   $211.00  
  7 purchase totals = $771.46       $851.5811   $851.59   $851.65   $851.40