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 $84.93   11.776%   $94.9314   $94.93   $94.95   $94.90  
  Purchase #2 $201.99   3.112%   $208.2759   $208.28   $208.30   $208.30  
  Purchase #3 $41.61   11.277%   $46.3024   $46.30   $46.30   $46.30  
  Purchase #4 $101.38   10.304%   $111.8262   $111.83   $111.85   $111.80  
  Purchase #5 $215.30   6.488%   $229.2687   $229.27   $229.25   $229.30  
  Purchase #6 $167.96   7.505%   $180.5654   $180.57   $180.55   $180.60  
  Purchase #7 $8.43   5.792%   $8.9183   $8.92   $8.90   $8.90  
  7 purchase totals = $821.60       $880.0883   $880.10   $880.10   $880.10