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 $114.26   9.716%   $125.3615   $125.36   $125.35   $125.40  
  Purchase #2 $191.25   13.774%   $217.5928   $217.59   $217.60   $217.60  
  Purchase #3 $51.37   6.533%   $54.726   $54.73   $54.75   $54.70  
  Purchase #4 $207.76   3.186%   $214.3792   $214.38   $214.40   $214.40  
  Purchase #5 $161.57   12.589%   $181.91   $181.91   $181.90   $181.90  
  Purchase #6 $118.75   8.215%   $128.5053   $128.51   $128.50   $128.50  
  Purchase #7 $109.65   13.874%   $124.8628   $124.86   $124.85   $124.90  
  7 purchase totals = $954.61       $1,047.3376   $1,047.34   $1,047.35   $1,047.40