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 $194.54   3.824%   $201.9792   $201.98   $202.00   $202.00  
  Purchase #2 $119.56   13.423%   $135.6085   $135.61   $135.60   $135.60  
  Purchase #3 $205.47   13.290%   $232.777   $232.78   $232.80   $232.80  
  Purchase #4 $46.47   6.629%   $49.5505   $49.55   $49.55   $49.60  
  Purchase #5 $186.89   5.562%   $197.2848   $197.28   $197.30   $197.30  
  Purchase #6 $19.89   5.678%   $21.0194   $21.02   $21.00   $21.00  
  Purchase #7 $192.49   5.302%   $202.6958   $202.70   $202.70   $202.70  
  7 purchase totals = $965.31       $1,040.9152   $1,040.92   $1,040.95   $1,041.00