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 $67.63   9.227%   $73.8702   $73.87   $73.85   $73.90  
  Purchase #2 $211.60   11.297%   $235.5045   $235.50   $235.50   $235.50  
  Purchase #3 $101.62   3.468%   $105.1442   $105.14   $105.15   $105.10  
  Purchase #4 $183.84   4.475%   $192.0668   $192.07   $192.05   $192.10  
  Purchase #5 $186.71   13.661%   $212.2165   $212.22   $212.20   $212.20  
  Purchase #6 $154.60   5.572%   $163.2143   $163.21   $163.20   $163.20  
  Purchase #7 $60.66   7.189%   $65.0208   $65.02   $65.00   $65.00  
  7 purchase totals = $966.66       $1,047.0373   $1,047.03   $1,046.95   $1,047.00