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 $95.32   9.126%   $104.0189   $104.02   $104.00   $104.00  
  Purchase #2 $98.34   6.499%   $104.7311   $104.73   $104.75   $104.70  
  Purchase #3 $241.52   6.800%   $257.9434   $257.94   $257.95   $257.90  
  Purchase #4 $151.74   8.212%   $164.2009   $164.20   $164.20   $164.20  
  Purchase #5 $229.70   6.552%   $244.7499   $244.75   $244.75   $244.70  
  Purchase #6 $214.37   9.135%   $233.9527   $233.95   $233.95   $234.00  
  Purchase #7 $243.63   9.584%   $266.9795   $266.98   $267.00   $267.00  
  7 purchase totals = $1,274.62       $1,376.5764   $1,376.57   $1,376.60   $1,376.50