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 $116.62   7.238%   $125.061   $125.06   $125.05   $125.10  
  Purchase #2 $108.45   13.170%   $122.7329   $122.73   $122.75   $122.70  
  Purchase #3 $26.69   6.838%   $28.5151   $28.52   $28.50   $28.50  
  Purchase #4 $158.49   5.852%   $167.7648   $167.76   $167.75   $167.80  
  Purchase #5 $237.50   7.312%   $254.866   $254.87   $254.85   $254.90  
  Purchase #6 $86.92   8.486%   $94.296   $94.30   $94.30   $94.30  
  Purchase #7 $209.65   5.794%   $221.7971   $221.80   $221.80   $221.80  
  7 purchase totals = $944.32       $1,015.0329   $1,015.04   $1,015.00   $1,015.10