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 $76.82   6.773%   $82.023   $82.02   $82.00   $82.00  
  Purchase #2 $117.93   13.528%   $133.8836   $133.88   $133.90   $133.90  
  Purchase #3 $141.72   8.569%   $153.864   $153.86   $153.85   $153.90  
  Purchase #4 $85.53   13.738%   $97.2801   $97.28   $97.30   $97.30  
  Purchase #5 $217.45   6.175%   $230.8775   $230.88   $230.90   $230.90  
  Purchase #6 $7.59   4.376%   $7.9221   $7.92   $7.90   $7.90  
  Purchase #7 $230.90   10.110%   $254.244   $254.24   $254.25   $254.20  
  7 purchase totals = $877.94       $960.0943   $960.08   $960.10   $960.10