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 $73.58   4.586%   $76.9544   $76.95   $76.95   $77.00  
  Purchase #2 $115.27   3.720%   $119.558   $119.56   $119.55   $119.60  
  Purchase #3 $176.52   9.257%   $192.8605   $192.86   $192.85   $192.90  
  Purchase #4 $58.73   12.231%   $65.9133   $65.91   $65.90   $65.90  
  Purchase #5 $113.74   10.289%   $125.4427   $125.44   $125.45   $125.40  
  Purchase #6 $92.36   6.110%   $98.0032   $98.00   $98.00   $98.00  
  Purchase #7 $38.34   7.284%   $41.1327   $41.13   $41.15   $41.10  
  7 purchase totals = $668.54       $719.8648   $719.85   $719.85   $719.90