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 $94.58   9.594%   $103.654   $103.65   $103.65   $103.70  
  Purchase #2 $235.81   3.721%   $244.5845   $244.58   $244.60   $244.60  
  Purchase #3 $111.38   3.559%   $115.344   $115.34   $115.35   $115.30  
  Purchase #4 $126.60   8.383%   $137.2129   $137.21   $137.20   $137.20  
  Purchase #5 $169.53   5.542%   $178.9254   $178.93   $178.95   $178.90  
  Purchase #6 $205.88   9.396%   $225.2245   $225.22   $225.20   $225.20  
  Purchase #7 $60.65   12.688%   $68.3453   $68.35   $68.35   $68.30  
  7 purchase totals = $1,004.43       $1,073.2906   $1,073.28   $1,073.30   $1,073.20