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 $225.81   6.785%   $241.1312   $241.13   $241.15   $241.10  
  Purchase #2 $149.92   5.637%   $158.371   $158.37   $158.35   $158.40  
  Purchase #3 $56.86   5.856%   $60.1897   $60.19   $60.20   $60.20  
  Purchase #4 $218.99   6.295%   $232.7754   $232.78   $232.80   $232.80  
  Purchase #5 $156.74   7.228%   $168.0692   $168.07   $168.05   $168.10  
  Purchase #6 $104.38   3.437%   $107.9675   $107.97   $107.95   $108.00  
  Purchase #7 $127.87   10.786%   $141.6621   $141.66   $141.65   $141.70  
  7 purchase totals = $1,040.57       $1,110.1661   $1,110.17   $1,110.15   $1,110.30