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 $12.94   8.576%   $14.0497   $14.05   $14.05   $14.00  
  Purchase #2 $241.73   13.532%   $274.4409   $274.44   $274.45   $274.40  
  Purchase #3 $242.60   10.786%   $268.7668   $268.77   $268.75   $268.80  
  Purchase #4 $178.31   9.266%   $194.8322   $194.83   $194.85   $194.80  
  Purchase #5 $54.58   4.267%   $56.9089   $56.91   $56.90   $56.90  
  Purchase #6 $145.64   5.355%   $153.439   $153.44   $153.45   $153.40  
  Purchase #7 $126.53   4.286%   $131.9531   $131.95   $131.95   $132.00  
  7 purchase totals = $1,002.33       $1,094.3906   $1,094.39   $1,094.40   $1,094.30