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 $228.62   7.597%   $245.9883   $245.99   $246.00   $246.00  
  Purchase #2 $107.60   13.413%   $122.0324   $122.03   $122.05   $122.00  
  Purchase #3 $240.83   10.800%   $266.8396   $266.84   $266.85   $266.80  
  Purchase #4 $214.66   5.440%   $226.3375   $226.34   $226.35   $226.30  
  Purchase #5 $46.53   11.568%   $51.9126   $51.91   $51.90   $51.90  
  Purchase #6 $88.30   6.652%   $94.1737   $94.17   $94.15   $94.20  
  Purchase #7 $211.79   7.605%   $227.8966   $227.90   $227.90   $227.90  
  7 purchase totals = $1,138.33       $1,235.1807   $1,235.18   $1,235.20   $1,235.10