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 $175.74   5.690%   $185.7396   $185.74   $185.75   $185.70  
  Purchase #2 $246.56   5.110%   $259.1592   $259.16   $259.15   $259.20  
  Purchase #3 $69.81   9.102%   $76.1641   $76.16   $76.15   $76.20  
  Purchase #4 $233.95   4.580%   $244.6649   $244.66   $244.65   $244.70  
  Purchase #5 $203.83   3.633%   $211.2351   $211.24   $211.25   $211.20  
  Purchase #6 $46.44   11.381%   $51.7253   $51.73   $51.75   $51.70  
  Purchase #7 $241.35   11.294%   $268.6081   $268.61   $268.60   $268.60  
  7 purchase totals = $1,217.68       $1,297.2963   $1,297.30   $1,297.30   $1,297.30