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 $110.34   7.420%   $118.5272   $118.53   $118.55   $118.50  
  Purchase #2 $202.90   6.143%   $215.3641   $215.36   $215.35   $215.40  
  Purchase #3 $135.55   10.426%   $149.6824   $149.68   $149.70   $149.70  
  Purchase #4 $95.54   9.108%   $104.2418   $104.24   $104.25   $104.20  
  Purchase #5 $16.66   6.177%   $17.6891   $17.69   $17.70   $17.70  
  Purchase #6 $201.81   4.233%   $210.3526   $210.35   $210.35   $210.40  
  Purchase #7 $109.54   7.816%   $118.1016   $118.10   $118.10   $118.10  
  7 purchase totals = $872.34       $933.9588   $933.95   $934.00   $934.00