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 $175.81   10.558%   $194.372   $194.37   $194.35   $194.40  
  Purchase #2 $90.74   5.847%   $96.0456   $96.05   $96.05   $96.00  
  Purchase #3 $248.91   9.133%   $271.643   $271.64   $271.65   $271.60  
  Purchase #4 $248.58   11.131%   $276.2494   $276.25   $276.25   $276.20  
  Purchase #5 $236.38   3.594%   $244.8755   $244.88   $244.90   $244.90  
  Purchase #6 $183.47   11.329%   $204.2553   $204.26   $204.25   $204.30  
  Purchase #7 $239.81   8.667%   $260.5943   $260.59   $260.60   $260.60  
  7 purchase totals = $1,423.70       $1,548.0351   $1,548.04   $1,548.05   $1,548.00