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 $183.33   6.511%   $195.2666   $195.27   $195.25   $195.30  
  Purchase #2 $203.31   9.778%   $223.1897   $223.19   $223.20   $223.20  
  Purchase #3 $16.87   6.636%   $17.9895   $17.99   $18.00   $18.00  
  Purchase #4 $219.71   5.357%   $231.4799   $231.48   $231.50   $231.50  
  Purchase #5 $95.50   3.414%   $98.7604   $98.76   $98.75   $98.80  
  Purchase #6 $149.38   7.526%   $160.6223   $160.62   $160.60   $160.60  
  Purchase #7 $129.27   12.634%   $145.602   $145.60   $145.60   $145.60  
  7 purchase totals = $997.37       $1,072.9104   $1,072.91   $1,072.90   $1,073.00