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 $84.76   11.689%   $94.6676   $94.67   $94.65   $94.70  
  Purchase #2 $221.55   3.637%   $229.6078   $229.61   $229.60   $229.60  
  Purchase #3 $238.67   13.613%   $271.1601   $271.16   $271.15   $271.20  
  Purchase #4 $141.93   3.407%   $146.7656   $146.77   $146.75   $146.80  
  Purchase #5 $154.35   9.435%   $168.9129   $168.91   $168.90   $168.90  
  Purchase #6 $16.40   5.265%   $17.2635   $17.26   $17.25   $17.30  
  Purchase #7 $176.78   3.764%   $183.434   $183.43   $183.45   $183.40  
  7 purchase totals = $1,034.44       $1,111.8115   $1,111.81   $1,111.75   $1,111.90