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 $175.48   11.152%   $195.0495   $195.05   $195.05   $195.00  
  Purchase #2 $102.29   3.131%   $105.4927   $105.49   $105.50   $105.50  
  Purchase #3 $241.87   11.593%   $269.91   $269.91   $269.90   $269.90  
  Purchase #4 $197.51   7.515%   $212.3529   $212.35   $212.35   $212.40  
  Purchase #5 $160.28   6.600%   $170.8585   $170.86   $170.85   $170.90  
  Purchase #6 $157.37   12.411%   $176.9012   $176.90   $176.90   $176.90  
  Purchase #7 $178.31   11.696%   $199.1651   $199.17   $199.15   $199.20  
  7 purchase totals = $1,213.11       $1,329.7299   $1,329.73   $1,329.70   $1,329.80