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 $84.76   13.468%   $96.1755   $96.18   $96.20   $96.20  
  Purchase #2 $170.48   8.245%   $184.5361   $184.54   $184.55   $184.50  
  Purchase #3 $205.59   11.355%   $228.9347   $228.93   $228.95   $228.90  
  Purchase #4 $248.25   4.191%   $258.6542   $258.65   $258.65   $258.70  
  Purchase #5 $149.32   10.190%   $164.5357   $164.54   $164.55   $164.50  
  Purchase #6 $245.49   6.272%   $260.8871   $260.89   $260.90   $260.90  
  Purchase #7 $240.28   13.169%   $271.9225   $271.92   $271.90   $271.90  
  7 purchase totals = $1,344.17       $1,465.6458   $1,465.65   $1,465.70   $1,465.60