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 $211.39   10.795%   $234.2096   $234.21   $234.20   $234.20  
  Purchase #2 $54.98   11.757%   $61.444   $61.44   $61.45   $61.40  
  Purchase #3 $44.74   7.272%   $47.9935   $47.99   $48.00   $48.00  
  Purchase #4 $147.47   7.283%   $158.2102   $158.21   $158.20   $158.20  
  Purchase #5 $31.96   11.468%   $35.6252   $35.63   $35.65   $35.60  
  Purchase #6 $221.65   13.481%   $251.5306   $251.53   $251.55   $251.50  
  Purchase #7 $241.46   8.443%   $261.8465   $261.85   $261.85   $261.80  
  7 purchase totals = $953.65       $1,050.8596   $1,050.86   $1,050.90   $1,050.70