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 $60.50   3.233%   $62.456   $62.46   $62.45   $62.50  
  Purchase #2 $84.87   12.630%   $95.5891   $95.59   $95.60   $95.60  
  Purchase #3 $206.30   9.200%   $225.2796   $225.28   $225.30   $225.30  
  Purchase #4 $169.76   12.677%   $191.2805   $191.28   $191.30   $191.30  
  Purchase #5 $29.84   7.526%   $32.0858   $32.09   $32.10   $32.10  
  Purchase #6 $84.83   12.645%   $95.5568   $95.56   $95.55   $95.60  
  Purchase #7 $240.85   8.815%   $262.0809   $262.08   $262.10   $262.10  
  7 purchase totals = $876.95       $964.3287   $964.34   $964.40   $964.50