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 $85.87   8.367%   $93.0547   $93.05   $93.05   $93.10  
  Purchase #2 $156.97   11.863%   $175.5914   $175.59   $175.60   $175.60  
  Purchase #3 $115.69   13.431%   $131.2283   $131.23   $131.25   $131.20  
  Purchase #4 $91.70   3.267%   $94.6958   $94.70   $94.70   $94.70  
  Purchase #5 $180.98   8.365%   $196.119   $196.12   $196.10   $196.10  
  Purchase #6 $51.44   8.414%   $55.7682   $55.77   $55.75   $55.80  
  Purchase #7 $189.70   5.491%   $200.1164   $200.12   $200.10   $200.10  
  7 purchase totals = $872.35       $946.5738   $946.58   $946.55   $946.60