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 $83.34   13.625%   $94.6951   $94.70   $94.70   $94.70  
  Purchase #2 $62.93   4.560%   $65.7996   $65.80   $65.80   $65.80  
  Purchase #3 $158.75   10.746%   $175.8093   $175.81   $175.80   $175.80  
  Purchase #4 $77.70   13.120%   $87.8942   $87.89   $87.90   $87.90  
  Purchase #5 $169.48   13.736%   $192.7598   $192.76   $192.75   $192.80  
  Purchase #6 $86.60   3.817%   $89.9055   $89.91   $89.90   $89.90  
  Purchase #7 $216.86   13.510%   $246.1578   $246.16   $246.15   $246.20  
  7 purchase totals = $855.66       $953.0213   $953.03   $953.00   $953.10