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 $147.36   10.143%   $162.3067   $162.31   $162.30   $162.30  
  Purchase #2 $224.65   9.575%   $246.1602   $246.16   $246.15   $246.20  
  Purchase #3 $57.99   11.358%   $64.5765   $64.58   $64.60   $64.60  
  Purchase #4 $250.53   9.245%   $273.6915   $273.69   $273.70   $273.70  
  Purchase #5 $65.38   11.148%   $72.6686   $72.67   $72.65   $72.70  
  Purchase #6 $175.96   5.229%   $185.1609   $185.16   $185.15   $185.20  
  Purchase #7 $237.39   10.246%   $261.713   $261.71   $261.70   $261.70  
  7 purchase totals = $1,159.26       $1,266.2774   $1,266.28   $1,266.25   $1,266.40