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 $232.39   6.567%   $247.6511   $247.65   $247.65   $247.70  
  Purchase #2 $181.35   7.348%   $194.6756   $194.68   $194.70   $194.70  
  Purchase #3 $119.52   5.516%   $126.1127   $126.11   $126.10   $126.10  
  Purchase #4 $168.83   7.863%   $182.1051   $182.11   $182.10   $182.10  
  Purchase #5 $96.92   5.776%   $102.5181   $102.52   $102.50   $102.50  
  Purchase #6 $151.38   4.128%   $157.629   $157.63   $157.65   $157.60  
  Purchase #7 $185.34   7.476%   $199.196   $199.20   $199.20   $199.20  
  7 purchase totals = $1,135.73       $1,209.8876   $1,209.90   $1,209.90   $1,209.90