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 $173.62   12.841%   $195.9145   $195.91   $195.90   $195.90  
  Purchase #2 $69.63   9.411%   $76.1829   $76.18   $76.20   $76.20  
  Purchase #3 $95.41   11.209%   $106.1045   $106.10   $106.10   $106.10  
  Purchase #4 $213.47   6.299%   $226.9165   $226.92   $226.90   $226.90  
  Purchase #5 $152.41   9.224%   $166.4683   $166.47   $166.45   $166.50  
  Purchase #6 $218.66   8.453%   $237.1433   $237.14   $237.15   $237.10  
  Purchase #7 $13.60   10.486%   $15.0261   $15.03   $15.05   $15.00  
  7 purchase totals = $936.80       $1,023.7561   $1,023.75   $1,023.75   $1,023.70