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 $148.62   5.808%   $157.2518   $157.25   $157.25   $157.30  
  Purchase #2 $111.41   3.648%   $115.4742   $115.47   $115.45   $115.50  
  Purchase #3 $95.27   6.446%   $101.4111   $101.41   $101.40   $101.40  
  Purchase #4 $158.97   3.388%   $164.3559   $164.36   $164.35   $164.40  
  Purchase #5 $195.59   5.686%   $206.7112   $206.71   $206.70   $206.70  
  Purchase #6 $127.72   13.474%   $144.929   $144.93   $144.95   $144.90  
  Purchase #7 $191.43   7.181%   $205.1766   $205.18   $205.20   $205.20  
  7 purchase totals = $1,029.01       $1,095.3098   $1,095.31   $1,095.30   $1,095.40