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 $194.84   6.223%   $206.9649   $206.96   $206.95   $207.00  
  Purchase #2 $229.53   9.105%   $250.4287   $250.43   $250.45   $250.40  
  Purchase #3 $242.92   5.530%   $256.3535   $256.35   $256.35   $256.40  
  Purchase #4 $49.33   10.414%   $54.4672   $54.47   $54.45   $54.50  
  Purchase #5 $139.63   4.672%   $146.1535   $146.15   $146.15   $146.20  
  Purchase #6 $56.53   11.706%   $63.1474   $63.15   $63.15   $63.10  
  Purchase #7 $132.33   6.661%   $141.1445   $141.14   $141.15   $141.10  
  7 purchase totals = $1,045.11       $1,118.6597   $1,118.65   $1,118.65   $1,118.70