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 $44.56   5.312%   $46.927   $46.93   $46.95   $46.90  
  Purchase #2 $187.78   5.577%   $198.2525   $198.25   $198.25   $198.30  
  Purchase #3 $73.71   4.445%   $76.9864   $76.99   $77.00   $77.00  
  Purchase #4 $95.89   3.794%   $99.5281   $99.53   $99.55   $99.50  
  Purchase #5 $31.48   6.644%   $33.5715   $33.57   $33.55   $33.60  
  Purchase #6 $217.43   10.121%   $239.4361   $239.44   $239.45   $239.40  
  Purchase #7 $143.85   3.767%   $149.2688   $149.27   $149.25   $149.30  
  7 purchase totals = $794.70       $843.9704   $843.98   $844.00   $844.00