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 $93.53   3.681%   $96.9728   $96.97   $96.95   $97.00  
  Purchase #2 $221.90   10.117%   $244.3496   $244.35   $244.35   $244.30  
  Purchase #3 $109.55   3.488%   $113.3711   $113.37   $113.35   $113.40  
  Purchase #4 $126.67   5.457%   $133.5824   $133.58   $133.60   $133.60  
  Purchase #5 $195.90   4.647%   $205.0035   $205.00   $205.00   $205.00  
  Purchase #6 $101.51   11.630%   $113.3156   $113.32   $113.30   $113.30  
  Purchase #7 $69.77   7.438%   $74.9595   $74.96   $74.95   $75.00  
  7 purchase totals = $918.83       $981.5545   $981.55   $981.50   $981.60