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 $162.98   6.842%   $174.1311   $174.13   $174.15   $174.10  
  Purchase #2 $215.68   10.776%   $238.9217   $238.92   $238.90   $238.90  
  Purchase #3 $92.48   10.476%   $102.1682   $102.17   $102.15   $102.20  
  Purchase #4 $76.82   10.105%   $84.5827   $84.58   $84.60   $84.60  
  Purchase #5 $205.42   12.833%   $231.7815   $231.78   $231.80   $231.80  
  Purchase #6 $219.43   6.423%   $233.524   $233.52   $233.50   $233.50  
  Purchase #7 $193.46   8.857%   $210.5948   $210.59   $210.60   $210.60  
  7 purchase totals = $1,166.27       $1,275.7040   $1,275.69   $1,275.70   $1,275.70