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 $76.34   12.796%   $86.1085   $86.11   $86.10   $86.10  
  Purchase #2 $118.45   12.361%   $133.0916   $133.09   $133.10   $133.10  
  Purchase #3 $44.84   4.256%   $46.7484   $46.75   $46.75   $46.70  
  Purchase #4 $58.26   4.865%   $61.0943   $61.09   $61.10   $61.10  
  Purchase #5 $229.75   4.843%   $240.8768   $240.88   $240.90   $240.90  
  Purchase #6 $247.45   11.211%   $275.1916   $275.19   $275.20   $275.20  
  Purchase #7 $101.43   4.842%   $106.3412   $106.34   $106.35   $106.30  
  7 purchase totals = $876.52       $949.4524   $949.45   $949.50   $949.40