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 $57.46   8.732%   $62.4774   $62.48   $62.50   $62.50  
  Purchase #2 $209.51   11.597%   $233.8069   $233.81   $233.80   $233.80  
  Purchase #3 $126.82   10.567%   $140.2211   $140.22   $140.20   $140.20  
  Purchase #4 $117.80   7.563%   $126.7092   $126.71   $126.70   $126.70  
  Purchase #5 $194.33   7.483%   $208.8717   $208.87   $208.85   $208.90  
  Purchase #6 $173.43   10.725%   $192.0304   $192.03   $192.05   $192.00  
  Purchase #7 $231.86   4.141%   $241.4613   $241.46   $241.45   $241.50  
  7 purchase totals = $1,111.21       $1,205.5780   $1,205.58   $1,205.55   $1,205.60