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 $195.79   6.272%   $208.0699   $208.07   $208.05   $208.10  
  Purchase #2 $204.50   11.780%   $228.5901   $228.59   $228.60   $228.60  
  Purchase #3 $214.37   4.335%   $223.6629   $223.66   $223.65   $223.70  
  Purchase #4 $131.76   7.235%   $141.2928   $141.29   $141.30   $141.30  
  Purchase #5 $125.52   13.568%   $142.5506   $142.55   $142.55   $142.60  
  Purchase #6 $178.31   3.147%   $183.9214   $183.92   $183.90   $183.90  
  Purchase #7 $211.47   4.798%   $221.6163   $221.62   $221.60   $221.60  
  7 purchase totals = $1,261.72       $1,349.7040   $1,349.70   $1,349.65   $1,349.80