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 $87.33   8.552%   $94.7985   $94.80   $94.80   $94.80  
  Purchase #2 $10.81   3.353%   $11.1725   $11.17   $11.15   $11.20  
  Purchase #3 $175.58   10.673%   $194.3197   $194.32   $194.30   $194.30  
  Purchase #4 $234.84   10.635%   $259.8152   $259.82   $259.80   $259.80  
  Purchase #5 $57.62   12.635%   $64.9003   $64.90   $64.90   $64.90  
  Purchase #6 $72.76   9.469%   $79.6496   $79.65   $79.65   $79.60  
  Purchase #7 $95.77   4.823%   $100.389   $100.39   $100.40   $100.40  
  7 purchase totals = $734.71       $805.0448   $805.05   $805.00   $805.00