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 $23.53   11.579%   $26.2545   $26.25   $26.25   $26.30  
  Purchase #2 $124.96   9.217%   $136.4776   $136.48   $136.50   $136.50  
  Purchase #3 $113.39   9.434%   $124.0872   $124.09   $124.10   $124.10  
  Purchase #4 $199.31   5.264%   $209.8017   $209.80   $209.80   $209.80  
  Purchase #5 $169.48   10.458%   $187.2042   $187.20   $187.20   $187.20  
  Purchase #6 $204.69   4.749%   $214.4107   $214.41   $214.40   $214.40  
  Purchase #7 $234.76   8.174%   $253.9493   $253.95   $253.95   $253.90  
  7 purchase totals = $1,070.12       $1,152.1852   $1,152.18   $1,152.20   $1,152.20