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 $44.40   9.320%   $48.5381   $48.54   $48.55   $48.50  
  Purchase #2 $119.56   10.420%   $132.0182   $132.02   $132.00   $132.00  
  Purchase #3 $196.83   10.609%   $217.7117   $217.71   $217.70   $217.70  
  Purchase #4 $206.40   9.474%   $225.9543   $225.95   $225.95   $226.00  
  Purchase #5 $185.43   5.532%   $195.688   $195.69   $195.70   $195.70  
  Purchase #6 $178.27   12.862%   $201.1991   $201.20   $201.20   $201.20  
  Purchase #7 $24.83   10.638%   $27.4714   $27.47   $27.45   $27.50  
  7 purchase totals = $955.72       $1,048.5808   $1,048.58   $1,048.55   $1,048.60