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 $55.61   12.602%   $62.618   $62.62   $62.60   $62.60  
  Purchase #2 $161.35   5.103%   $169.5837   $169.58   $169.60   $169.60  
  Purchase #3 $155.25   9.473%   $169.9568   $169.96   $169.95   $170.00  
  Purchase #4 $25.49   3.293%   $26.3294   $26.33   $26.35   $26.30  
  Purchase #5 $246.73   11.244%   $274.4723   $274.47   $274.45   $274.50  
  Purchase #6 $29.99   4.689%   $31.3962   $31.40   $31.40   $31.40  
  Purchase #7 $23.69   10.398%   $26.1533   $26.15   $26.15   $26.20  
  7 purchase totals = $698.11       $760.5097   $760.51   $760.50   $760.60