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 $202.41   11.660%   $226.011   $226.01   $226.00   $226.00  
  Purchase #2 $75.55   8.543%   $82.0042   $82.00   $82.00   $82.00  
  Purchase #3 $49.56   5.154%   $52.1143   $52.11   $52.10   $52.10  
  Purchase #4 $236.27   4.435%   $246.7486   $246.75   $246.75   $246.70  
  Purchase #5 $179.69   11.177%   $199.774   $199.77   $199.75   $199.80  
  Purchase #6 $121.69   10.503%   $134.4711   $134.47   $134.45   $134.50  
  Purchase #7 $247.47   11.485%   $275.8919   $275.89   $275.90   $275.90  
  7 purchase totals = $1,112.64       $1,217.0151   $1,217.00   $1,216.95   $1,217.00