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 $90.36   5.203%   $95.0614   $95.06   $95.05   $95.10  
  Purchase #2 $163.30   6.473%   $173.8704   $173.87   $173.85   $173.90  
  Purchase #3 $215.69   11.606%   $240.723   $240.72   $240.70   $240.70  
  Purchase #4 $129.37   3.873%   $134.3805   $134.38   $134.40   $134.40  
  Purchase #5 $214.53   3.237%   $221.4743   $221.47   $221.45   $221.50  
  Purchase #6 $247.41   8.522%   $268.4943   $268.49   $268.50   $268.50  
  Purchase #7 $152.92   4.546%   $159.8717   $159.87   $159.85   $159.90  
  7 purchase totals = $1,213.58       $1,293.8756   $1,293.86   $1,293.80   $1,294.00