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 $241.72   8.757%   $262.8874   $262.89   $262.90   $262.90  
  Purchase #2 $217.64   3.268%   $224.7525   $224.75   $224.75   $224.80  
  Purchase #3 $205.31   13.135%   $232.2775   $232.28   $232.30   $232.30  
  Purchase #4 $59.33   3.660%   $61.5015   $61.50   $61.50   $61.50  
  Purchase #5 $127.34   5.589%   $134.457   $134.46   $134.45   $134.50  
  Purchase #6 $141.75   13.811%   $161.3271   $161.33   $161.35   $161.30  
  Purchase #7 $112.54   13.483%   $127.7138   $127.71   $127.70   $127.70  
  7 purchase totals = $1,105.63       $1,204.9168   $1,204.92   $1,204.95   $1,205.00