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 $68.95   8.787%   $75.0086   $75.01   $75.00   $75.00  
  Purchase #2 $224.51   3.177%   $231.6427   $231.64   $231.65   $231.60  
  Purchase #3 $173.73   11.263%   $193.2972   $193.30   $193.30   $193.30  
  Purchase #4 $101.27   5.556%   $106.8966   $106.90   $106.90   $106.90  
  Purchase #5 $201.43   8.154%   $217.8546   $217.85   $217.85   $217.90  
  Purchase #6 $125.31   9.713%   $137.4814   $137.48   $137.50   $137.50  
  Purchase #7 $213.61   12.554%   $240.4266   $240.43   $240.45   $240.40  
  7 purchase totals = $1,108.81       $1,202.6077   $1,202.61   $1,202.65   $1,202.60