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 $62.75   8.820%   $68.2846   $68.28   $68.30   $68.30  
  Purchase #2 $119.87   4.723%   $125.5315   $125.53   $125.55   $125.50  
  Purchase #3 $22.74   8.732%   $24.7257   $24.73   $24.75   $24.70  
  Purchase #4 $212.65   6.554%   $226.5871   $226.59   $226.60   $226.60  
  Purchase #5 $224.95   12.526%   $253.1272   $253.13   $253.15   $253.10  
  Purchase #6 $142.89   11.452%   $159.2538   $159.25   $159.25   $159.30  
  Purchase #7 $143.45   9.798%   $157.5052   $157.51   $157.50   $157.50  
  7 purchase totals = $929.30       $1,015.0151   $1,015.02   $1,015.10   $1,015.00