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 $69.44   8.294%   $75.1994   $75.20   $75.20   $75.20  
  Purchase #2 $197.38   3.613%   $204.5113   $204.51   $204.50   $204.50  
  Purchase #3 $164.70   6.279%   $175.0415   $175.04   $175.05   $175.00  
  Purchase #4 $93.84   4.170%   $97.7531   $97.75   $97.75   $97.80  
  Purchase #5 $129.35   13.288%   $146.538   $146.54   $146.55   $146.50  
  Purchase #6 $142.92   3.666%   $148.1594   $148.16   $148.15   $148.20  
  Purchase #7 $114.86   4.554%   $120.0907   $120.09   $120.10   $120.10  
  7 purchase totals = $912.49       $967.2934   $967.29   $967.30   $967.30