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 $175.53   6.555%   $187.036   $187.04   $187.05   $187.00  
  Purchase #2 $112.68   5.264%   $118.6115   $118.61   $118.60   $118.60  
  Purchase #3 $176.95   9.311%   $193.4258   $193.43   $193.45   $193.40  
  Purchase #4 $127.84   4.151%   $133.1466   $133.15   $133.15   $133.10  
  Purchase #5 $170.65   9.499%   $186.86   $186.86   $186.85   $186.90  
  Purchase #6 $113.63   6.514%   $121.0319   $121.03   $121.05   $121.00  
  Purchase #7 $218.82   5.707%   $231.3081   $231.31   $231.30   $231.30  
  7 purchase totals = $1,096.10       $1,171.4199   $1,171.43   $1,171.45   $1,171.30