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 $24.58   5.787%   $26.0024   $26.00   $26.00   $26.00  
  Purchase #2 $198.98   6.614%   $212.1405   $212.14   $212.15   $212.10  
  Purchase #3 $248.79   10.619%   $275.209   $275.21   $275.20   $275.20  
  Purchase #4 $11.33   3.267%   $11.7002   $11.70   $11.70   $11.70  
  Purchase #5 $48.82   8.823%   $53.1274   $53.13   $53.15   $53.10  
  Purchase #6 $18.97   13.316%   $21.496   $21.50   $21.50   $21.50  
  Purchase #7 $139.98   3.596%   $145.0137   $145.01   $145.00   $145.00  
  7 purchase totals = $691.45       $744.6892   $744.69   $744.70   $744.60