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 $174.43   12.525%   $196.2774   $196.28   $196.30   $196.30  
  Purchase #2 $94.61   11.686%   $105.6661   $105.67   $105.65   $105.70  
  Purchase #3 $44.69   3.775%   $46.377   $46.38   $46.40   $46.40  
  Purchase #4 $46.91   10.654%   $51.9078   $51.91   $51.90   $51.90  
  Purchase #5 $126.25   7.274%   $135.4334   $135.43   $135.45   $135.40  
  Purchase #6 $7.39   5.450%   $7.7928   $7.79   $7.80   $7.80  
  Purchase #7 $181.93   4.181%   $189.5365   $189.54   $189.55   $189.50  
  7 purchase totals = $676.21       $732.9910   $733.00   $733.05   $733.00