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 $185.26   5.616%   $195.6642   $195.66   $195.65   $195.70  
  Purchase #2 $237.69   5.848%   $251.5901   $251.59   $251.60   $251.60  
  Purchase #3 $58.55   5.477%   $61.7568   $61.76   $61.75   $61.80  
  Purchase #4 $10.38   11.782%   $11.603   $11.60   $11.60   $11.60  
  Purchase #5 $28.60   13.223%   $32.3818   $32.38   $32.40   $32.40  
  Purchase #6 $244.59   10.843%   $271.1109   $271.11   $271.10   $271.10  
  Purchase #7 $16.58   4.465%   $17.3203   $17.32   $17.30   $17.30  
  7 purchase totals = $781.65       $841.4271   $841.42   $841.40   $841.50