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 $57.86   3.476%   $59.8712   $59.87   $59.85   $59.90  
  Purchase #2 $125.80   12.566%   $141.608   $141.61   $141.60   $141.60  
  Purchase #3 $80.90   10.144%   $89.1065   $89.11   $89.10   $89.10  
  Purchase #4 $212.77   8.531%   $230.9214   $230.92   $230.90   $230.90  
  Purchase #5 $169.68   7.378%   $182.199   $182.20   $182.20   $182.20  
  Purchase #6 $250.97   12.535%   $282.4291   $282.43   $282.45   $282.40  
  Purchase #7 $188.97   9.455%   $206.8371   $206.84   $206.85   $206.80  
  7 purchase totals = $1,086.95       $1,192.9723   $1,192.98   $1,192.95   $1,192.90