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 $198.63   6.213%   $210.9709   $210.97   $210.95   $211.00  
  Purchase #2 $200.40   8.424%   $217.2817   $217.28   $217.30   $217.30  
  Purchase #3 $58.91   4.864%   $61.7754   $61.78   $61.80   $61.80  
  Purchase #4 $57.56   9.237%   $62.8768   $62.88   $62.90   $62.90  
  Purchase #5 $26.74   3.308%   $27.6246   $27.62   $27.60   $27.60  
  Purchase #6 $247.73   5.428%   $261.1768   $261.18   $261.20   $261.20  
  Purchase #7 $242.61   7.759%   $261.4341   $261.43   $261.45   $261.40  
  7 purchase totals = $1,032.58       $1,103.1403   $1,103.14   $1,103.20   $1,103.20