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 $43.45   10.357%   $47.9501   $47.95   $47.95   $48.00  
  Purchase #2 $143.79   9.458%   $157.3897   $157.39   $157.40   $157.40  
  Purchase #3 $212.98   4.220%   $221.9678   $221.97   $221.95   $222.00  
  Purchase #4 $173.99   7.680%   $187.3524   $187.35   $187.35   $187.40  
  Purchase #5 $129.74   8.398%   $140.6356   $140.64   $140.65   $140.60  
  Purchase #6 $207.43   9.707%   $227.5652   $227.57   $227.55   $227.60  
  Purchase #7 $66.26   11.230%   $73.701   $73.70   $73.70   $73.70  
  7 purchase totals = $977.64       $1,056.5618   $1,056.57   $1,056.55   $1,056.70