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 $23.86   8.802%   $25.9602   $25.96   $25.95   $26.00  
  Purchase #2 $84.44   4.231%   $88.0127   $88.01   $88.00   $88.00  
  Purchase #3 $151.58   7.542%   $163.0122   $163.01   $163.00   $163.00  
  Purchase #4 $123.71   3.471%   $128.004   $128.00   $128.00   $128.00  
  Purchase #5 $245.79   5.674%   $259.7361   $259.74   $259.75   $259.70  
  Purchase #6 $70.29   8.658%   $76.3757   $76.38   $76.40   $76.40  
  Purchase #7 $26.94   3.424%   $27.8624   $27.86   $27.85   $27.90  
  7 purchase totals = $726.61       $768.9633   $768.96   $768.95   $769.00