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 $245.88   8.659%   $267.1707   $267.17   $267.15   $267.20  
  Purchase #2 $112.54   13.148%   $127.3368   $127.34   $127.35   $127.30  
  Purchase #3 $23.63   5.331%   $24.8897   $24.89   $24.90   $24.90  
  Purchase #4 $218.53   6.284%   $232.2624   $232.26   $232.25   $232.30  
  Purchase #5 $217.42   5.131%   $228.5758   $228.58   $228.60   $228.60  
  Purchase #6 $208.56   4.639%   $218.2351   $218.24   $218.25   $218.20  
  Purchase #7 $91.30   13.240%   $103.3881   $103.39   $103.40   $103.40  
  7 purchase totals = $1,117.86       $1,201.8586   $1,201.87   $1,201.90   $1,201.90