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 $49.30   10.282%   $54.369   $54.37   $54.35   $54.40  
  Purchase #2 $86.56   5.143%   $91.0118   $91.01   $91.00   $91.00  
  Purchase #3 $139.40   9.701%   $152.9232   $152.92   $152.90   $152.90  
  Purchase #4 $72.56   3.636%   $75.1983   $75.20   $75.20   $75.20  
  Purchase #5 $175.37   11.588%   $195.6919   $195.69   $195.70   $195.70  
  Purchase #6 $187.78   13.640%   $213.3932   $213.39   $213.40   $213.40  
  Purchase #7 $242.75   7.861%   $261.8326   $261.83   $261.85   $261.80  
  7 purchase totals = $953.72       $1,044.4200   $1,044.41   $1,044.40   $1,044.40