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 $215.83   4.351%   $225.2208   $225.22   $225.20   $225.20  
  Purchase #2 $233.97   9.566%   $256.3516   $256.35   $256.35   $256.40  
  Purchase #3 $45.69   3.647%   $47.3563   $47.36   $47.35   $47.40  
  Purchase #4 $249.67   7.366%   $268.0607   $268.06   $268.05   $268.10  
  Purchase #5 $146.60   7.402%   $157.4513   $157.45   $157.45   $157.50  
  Purchase #6 $152.86   8.162%   $165.3364   $165.34   $165.35   $165.30  
  Purchase #7 $108.75   4.670%   $113.8286   $113.83   $113.85   $113.80  
  7 purchase totals = $1,153.37       $1,233.6057   $1,233.61   $1,233.60   $1,233.70