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 $195.82   13.541%   $222.336   $222.34   $222.35   $222.30  
  Purchase #2 $196.38   4.726%   $205.6609   $205.66   $205.65   $205.70  
  Purchase #3 $125.74   5.271%   $132.3678   $132.37   $132.35   $132.40  
  Purchase #4 $41.43   8.503%   $44.9528   $44.95   $44.95   $45.00  
  Purchase #5 $163.76   5.779%   $173.2237   $173.22   $173.20   $173.20  
  Purchase #6 $141.68   8.816%   $154.1705   $154.17   $154.15   $154.20  
  Purchase #7 $215.86   12.747%   $243.3757   $243.38   $243.40   $243.40  
  7 purchase totals = $1,080.67       $1,176.0874   $1,176.09   $1,176.05   $1,176.20