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 $104.26   5.416%   $109.9067   $109.91   $109.90   $109.90  
  Purchase #2 $24.36   4.131%   $25.3663   $25.37   $25.35   $25.40  
  Purchase #3 $159.66   11.165%   $177.486   $177.49   $177.50   $177.50  
  Purchase #4 $209.83   12.187%   $235.402   $235.40   $235.40   $235.40  
  Purchase #5 $182.33   12.430%   $204.9936   $204.99   $205.00   $205.00  
  Purchase #6 $124.44   6.792%   $132.892   $132.89   $132.90   $132.90  
  Purchase #7 $176.63   6.262%   $187.6906   $187.69   $187.70   $187.70  
  7 purchase totals = $981.51       $1,073.7372   $1,073.74   $1,073.75   $1,073.80