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 $210.58   8.620%   $228.732   $228.73   $228.75   $228.70  
  Purchase #2 $108.77   9.790%   $119.4186   $119.42   $119.40   $119.40  
  Purchase #3 $119.91   10.239%   $132.1876   $132.19   $132.20   $132.20  
  Purchase #4 $127.62   4.331%   $133.1472   $133.15   $133.15   $133.10  
  Purchase #5 $228.89   9.644%   $250.9642   $250.96   $250.95   $251.00  
  Purchase #6 $154.91   7.780%   $166.962   $166.96   $166.95   $167.00  
  Purchase #7 $156.64   4.597%   $163.8407   $163.84   $163.85   $163.80  
  7 purchase totals = $1,107.32       $1,195.2523   $1,195.25   $1,195.25   $1,195.20