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 $215.53   11.172%   $239.609   $239.61   $239.60   $239.60  
  Purchase #2 $204.80   3.218%   $211.3905   $211.39   $211.40   $211.40  
  Purchase #3 $60.35   3.789%   $62.6367   $62.64   $62.65   $62.60  
  Purchase #4 $242.65   4.596%   $253.8022   $253.80   $253.80   $253.80  
  Purchase #5 $43.38   3.853%   $45.0514   $45.05   $45.05   $45.10  
  Purchase #6 $104.67   12.655%   $117.916   $117.92   $117.90   $117.90  
  Purchase #7 $167.32   12.416%   $188.0945   $188.09   $188.10   $188.10  
  7 purchase totals = $1,038.70       $1,118.5003   $1,118.50   $1,118.50   $1,118.50