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 $181.87   10.794%   $201.501   $201.50   $201.50   $201.50  
  Purchase #2 $124.95   7.522%   $134.3487   $134.35   $134.35   $134.30  
  Purchase #3 $125.37   13.494%   $142.2874   $142.29   $142.30   $142.30  
  Purchase #4 $43.38   5.854%   $45.9195   $45.92   $45.90   $45.90  
  Purchase #5 $148.63   5.226%   $156.3974   $156.40   $156.40   $156.40  
  Purchase #6 $165.78   4.439%   $173.139   $173.14   $173.15   $173.10  
  Purchase #7 $198.32   8.355%   $214.8896   $214.89   $214.90   $214.90  
  7 purchase totals = $988.30       $1,068.4826   $1,068.49   $1,068.50   $1,068.40