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 $24.71   5.705%   $26.1197   $26.12   $26.10   $26.10  
  Purchase #2 $225.57   3.275%   $232.9574   $232.96   $232.95   $233.00  
  Purchase #3 $68.99   8.191%   $74.641   $74.64   $74.65   $74.60  
  Purchase #4 $57.59   5.105%   $60.53   $60.53   $60.55   $60.50  
  Purchase #5 $232.61   11.678%   $259.7742   $259.77   $259.75   $259.80  
  Purchase #6 $239.63   9.424%   $262.2127   $262.21   $262.20   $262.20  
  Purchase #7 $122.82   4.445%   $128.2793   $128.28   $128.30   $128.30  
  7 purchase totals = $971.92       $1,044.5143   $1,044.51   $1,044.50   $1,044.50