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 $67.49   5.287%   $71.0582   $71.06   $71.05   $71.10  
  Purchase #2 $89.99   5.818%   $95.2256   $95.23   $95.25   $95.20  
  Purchase #3 $183.78   4.813%   $192.6253   $192.63   $192.65   $192.60  
  Purchase #4 $25.79   10.532%   $28.5062   $28.51   $28.50   $28.50  
  Purchase #5 $49.95   4.857%   $52.3761   $52.38   $52.40   $52.40  
  Purchase #6 $229.99   10.743%   $254.6978   $254.70   $254.70   $254.70  
  Purchase #7 $23.34   5.151%   $24.5422   $24.54   $24.55   $24.50  
  7 purchase totals = $670.33       $719.0314   $719.05   $719.10   $719.00