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 $162.93   6.818%   $174.0386   $174.04   $174.05   $174.00  
  Purchase #2 $66.38   6.361%   $70.6024   $70.60   $70.60   $70.60  
  Purchase #3 $179.33   3.531%   $185.6621   $185.66   $185.65   $185.70  
  Purchase #4 $231.72   13.246%   $262.4136   $262.41   $262.40   $262.40  
  Purchase #5 $116.66   8.115%   $126.127   $126.13   $126.15   $126.10  
  Purchase #6 $121.48   10.212%   $133.8855   $133.89   $133.90   $133.90  
  Purchase #7 $202.72   10.307%   $223.6144   $223.61   $223.60   $223.60  
  7 purchase totals = $1,081.22       $1,176.3436   $1,176.34   $1,176.35   $1,176.30