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 $167.76   3.578%   $173.7625   $173.76   $173.75   $173.80  
  Purchase #2 $83.35   10.711%   $92.2776   $92.28   $92.30   $92.30  
  Purchase #3 $222.91   11.289%   $248.0743   $248.07   $248.05   $248.10  
  Purchase #4 $85.80   6.800%   $91.6344   $91.63   $91.65   $91.60  
  Purchase #5 $154.82   9.632%   $169.7323   $169.73   $169.75   $169.70  
  Purchase #6 $157.65   13.327%   $178.66   $178.66   $178.65   $178.70  
  Purchase #7 $55.95   7.754%   $60.2884   $60.29   $60.30   $60.30  
  7 purchase totals = $928.24       $1,014.4295   $1,014.42   $1,014.45   $1,014.50