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 $193.92   5.185%   $203.9748   $203.97   $203.95   $204.00  
  Purchase #2 $209.83   12.787%   $236.661   $236.66   $236.65   $236.70  
  Purchase #3 $224.41   3.796%   $232.9286   $232.93   $232.95   $232.90  
  Purchase #4 $183.42   8.132%   $198.3357   $198.34   $198.35   $198.30  
  Purchase #5 $63.60   4.430%   $66.4175   $66.42   $66.40   $66.40  
  Purchase #6 $49.27   9.797%   $54.097   $54.10   $54.10   $54.10  
  Purchase #7 $58.94   4.322%   $61.4874   $61.49   $61.50   $61.50  
  7 purchase totals = $983.39       $1,053.9020   $1,053.91   $1,053.90   $1,053.90