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 $84.73   13.754%   $96.3838   $96.38   $96.40   $96.40  
  Purchase #2 $217.65   12.289%   $244.397   $244.40   $244.40   $244.40  
  Purchase #3 $133.63   11.871%   $149.4932   $149.49   $149.50   $149.50  
  Purchase #4 $234.72   12.650%   $264.4121   $264.41   $264.40   $264.40  
  Purchase #5 $127.59   9.182%   $139.3053   $139.31   $139.30   $139.30  
  Purchase #6 $140.41   6.806%   $149.9663   $149.97   $149.95   $150.00  
  Purchase #7 $156.84   3.241%   $161.9232   $161.92   $161.90   $161.90  
  7 purchase totals = $1,095.57       $1,205.8809   $1,205.88   $1,205.85   $1,205.90