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 $108.65   5.176%   $114.2737   $114.27   $114.25   $114.30  
  Purchase #2 $71.46   5.350%   $75.2831   $75.28   $75.30   $75.30  
  Purchase #3 $88.33   8.666%   $95.9847   $95.98   $96.00   $96.00  
  Purchase #4 $215.48   9.318%   $235.5584   $235.56   $235.55   $235.60  
  Purchase #5 $105.36   6.555%   $112.2663   $112.27   $112.25   $112.30  
  Purchase #6 $113.78   5.754%   $120.3269   $120.33   $120.35   $120.30  
  Purchase #7 $62.43   11.629%   $69.69   $69.69   $69.70   $69.70  
  7 purchase totals = $765.49       $823.3831   $823.38   $823.40   $823.50