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 $178.98   11.194%   $199.015   $199.02   $199.00   $199.00  
  Purchase #2 $148.73   5.797%   $157.3519   $157.35   $157.35   $157.40  
  Purchase #3 $249.31   5.379%   $262.7204   $262.72   $262.70   $262.70  
  Purchase #4 $153.28   5.356%   $161.4897   $161.49   $161.50   $161.50  
  Purchase #5 $244.54   10.176%   $269.4244   $269.42   $269.40   $269.40  
  Purchase #6 $244.83   10.870%   $271.443   $271.44   $271.45   $271.40  
  Purchase #7 $132.86   10.847%   $147.2713   $147.27   $147.25   $147.30  
  7 purchase totals = $1,352.53       $1,468.7157   $1,468.71   $1,468.65   $1,468.70