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 $216.26   8.168%   $233.9241   $233.92   $233.90   $233.90  
  Purchase #2 $96.93   7.251%   $103.9584   $103.96   $103.95   $104.00  
  Purchase #3 $118.65   11.761%   $132.6044   $132.60   $132.60   $132.60  
  Purchase #4 $244.99   3.512%   $253.594   $253.59   $253.60   $253.60  
  Purchase #5 $223.64   6.573%   $238.3399   $238.34   $238.35   $238.30  
  Purchase #6 $214.81   10.712%   $237.8204   $237.82   $237.80   $237.80  
  Purchase #7 $91.29   12.307%   $102.5251   $102.53   $102.55   $102.50  
  7 purchase totals = $1,206.57       $1,302.7663   $1,302.76   $1,302.75   $1,302.70