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 $173.76   12.366%   $195.2472   $195.25   $195.25   $195.20  
  Purchase #2 $101.59   10.612%   $112.3707   $112.37   $112.35   $112.40  
  Purchase #3 $146.33   9.150%   $159.7192   $159.72   $159.70   $159.70  
  Purchase #4 $91.40   4.771%   $95.7607   $95.76   $95.75   $95.80  
  Purchase #5 $213.32   6.123%   $226.3816   $226.38   $226.40   $226.40  
  Purchase #6 $83.87   3.283%   $86.6235   $86.62   $86.60   $86.60  
  Purchase #7 $165.43   9.242%   $180.719   $180.72   $180.70   $180.70  
  7 purchase totals = $975.70       $1,056.8219   $1,056.82   $1,056.75   $1,056.80