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 $243.50   7.731%   $262.325   $262.33   $262.35   $262.30  
  Purchase #2 $112.47   6.634%   $119.9313   $119.93   $119.95   $119.90  
  Purchase #3 $180.88   8.186%   $195.6868   $195.69   $195.70   $195.70  
  Purchase #4 $13.48   13.802%   $15.3405   $15.34   $15.35   $15.30  
  Purchase #5 $165.60   6.754%   $176.7846   $176.78   $176.80   $176.80  
  Purchase #6 $171.64   9.774%   $188.4161   $188.42   $188.40   $188.40  
  Purchase #7 $47.34   9.112%   $51.6536   $51.65   $51.65   $51.70  
  7 purchase totals = $934.91       $1,010.1379   $1,010.14   $1,010.20   $1,010.10