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 $169.32   13.828%   $192.7336   $192.73   $192.75   $192.70  
  Purchase #2 $109.43   5.871%   $115.8546   $115.85   $115.85   $115.90  
  Purchase #3 $178.72   5.337%   $188.2583   $188.26   $188.25   $188.30  
  Purchase #4 $187.38   9.290%   $204.7876   $204.79   $204.80   $204.80  
  Purchase #5 $212.54   8.808%   $231.2605   $231.26   $231.25   $231.30  
  Purchase #6 $94.83   3.484%   $98.1339   $98.13   $98.15   $98.10  
  Purchase #7 $154.53   12.107%   $173.2389   $173.24   $173.25   $173.20  
  7 purchase totals = $1,106.75       $1,204.2674   $1,204.26   $1,204.30   $1,204.30