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 $55.60   10.468%   $61.4202   $61.42   $61.40   $61.40  
  Purchase #2 $69.47   10.355%   $76.6636   $76.66   $76.65   $76.70  
  Purchase #3 $202.46   5.485%   $213.5649   $213.56   $213.55   $213.60  
  Purchase #4 $173.91   10.282%   $191.7914   $191.79   $191.80   $191.80  
  Purchase #5 $132.29   9.201%   $144.462   $144.46   $144.45   $144.50  
  Purchase #6 $216.86   3.862%   $225.2351   $225.24   $225.25   $225.20  
  Purchase #7 $47.29   6.189%   $50.2168   $50.22   $50.20   $50.20  
  7 purchase totals = $897.88       $963.3540   $963.35   $963.30   $963.40