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 $182.25   9.294%   $199.1883   $199.19   $199.20   $199.20  
  Purchase #2 $89.68   5.769%   $94.8536   $94.85   $94.85   $94.90  
  Purchase #3 $207.32   6.776%   $221.368   $221.37   $221.35   $221.40  
  Purchase #4 $139.49   4.401%   $145.629   $145.63   $145.65   $145.60  
  Purchase #5 $162.53   7.625%   $174.9229   $174.92   $174.90   $174.90  
  Purchase #6 $171.36   4.788%   $179.5647   $179.56   $179.55   $179.60  
  Purchase #7 $182.72   5.703%   $193.1405   $193.14   $193.15   $193.10  
  7 purchase totals = $1,135.35       $1,208.6670   $1,208.66   $1,208.65   $1,208.70