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 $114.66   7.763%   $123.5611   $123.56   $123.55   $123.60  
  Purchase #2 $250.73   5.530%   $264.5954   $264.60   $264.60   $264.60  
  Purchase #3 $173.54   8.513%   $188.3135   $188.31   $188.30   $188.30  
  Purchase #4 $112.38   8.657%   $122.1087   $122.11   $122.10   $122.10  
  Purchase #5 $161.25   9.225%   $176.1253   $176.13   $176.15   $176.10  
  Purchase #6 $32.64   11.276%   $36.3205   $36.32   $36.30   $36.30  
  Purchase #7 $182.53   6.677%   $194.7175   $194.72   $194.70   $194.70  
  7 purchase totals = $1,027.73       $1,105.7420   $1,105.75   $1,105.70   $1,105.70