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 $224.99   7.123%   $241.016   $241.02   $241.00   $241.00  
  Purchase #2 $177.55   5.806%   $187.8586   $187.86   $187.85   $187.90  
  Purchase #3 $160.60   3.113%   $165.5995   $165.60   $165.60   $165.60  
  Purchase #4 $216.70   11.161%   $240.8859   $240.89   $240.90   $240.90  
  Purchase #5 $101.32   11.750%   $113.2251   $113.23   $113.25   $113.20  
  Purchase #6 $183.99   5.782%   $194.6283   $194.63   $194.65   $194.60  
  Purchase #7 $198.49   11.850%   $222.0111   $222.01   $222.00   $222.00  
  7 purchase totals = $1,263.64       $1,365.2245   $1,365.24   $1,365.25   $1,365.20