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 $205.49   9.515%   $225.0424   $225.04   $225.05   $225.00  
  Purchase #2 $21.46   5.408%   $22.6206   $22.62   $22.60   $22.60  
  Purchase #3 $243.98   4.393%   $254.698   $254.70   $254.70   $254.70  
  Purchase #4 $73.44   11.247%   $81.6998   $81.70   $81.70   $81.70  
  Purchase #5 $211.55   10.741%   $234.2726   $234.27   $234.25   $234.30  
  Purchase #6 $134.91   3.267%   $139.3175   $139.32   $139.30   $139.30  
  Purchase #7 $86.30   6.567%   $91.9673   $91.97   $91.95   $92.00  
  7 purchase totals = $977.13       $1,049.6182   $1,049.62   $1,049.55   $1,049.60