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 $201.54   6.795%   $215.2346   $215.23   $215.25   $215.20  
  Purchase #2 $196.45   4.727%   $205.7362   $205.74   $205.75   $205.70  
  Purchase #3 $59.98   5.104%   $63.0414   $63.04   $63.05   $63.00  
  Purchase #4 $77.82   11.313%   $86.6238   $86.62   $86.60   $86.60  
  Purchase #5 $82.38   3.392%   $85.1743   $85.17   $85.15   $85.20  
  Purchase #6 $9.42   4.247%   $9.8201   $9.82   $9.80   $9.80  
  Purchase #7 $87.74   10.526%   $96.9755   $96.98   $97.00   $97.00  
  7 purchase totals = $715.33       $762.6059   $762.60   $762.60   $762.50