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 $88.63   7.392%   $95.1815   $95.18   $95.20   $95.20  
  Purchase #2 $198.68   4.116%   $206.8577   $206.86   $206.85   $206.90  
  Purchase #3 $97.77   7.236%   $104.8446   $104.84   $104.85   $104.80  
  Purchase #4 $158.37   10.665%   $175.2602   $175.26   $175.25   $175.30  
  Purchase #5 $110.66   4.135%   $115.2358   $115.24   $115.25   $115.20  
  Purchase #6 $213.53   12.268%   $239.7259   $239.73   $239.75   $239.70  
  Purchase #7 $168.45   8.817%   $183.3022   $183.30   $183.30   $183.30  
  7 purchase totals = $1,036.09       $1,120.4079   $1,120.41   $1,120.45   $1,120.40