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 $207.95   10.363%   $229.4999   $229.50   $229.50   $229.50  
  Purchase #2 $247.42   10.828%   $274.2106   $274.21   $274.20   $274.20  
  Purchase #3 $161.32   7.688%   $173.7223   $173.72   $173.70   $173.70  
  Purchase #4 $98.99   11.815%   $110.6857   $110.69   $110.70   $110.70  
  Purchase #5 $246.69   8.829%   $268.4703   $268.47   $268.45   $268.50  
  Purchase #6 $241.40   7.687%   $259.9564   $259.96   $259.95   $260.00  
  Purchase #7 $115.96   7.713%   $124.904   $124.90   $124.90   $124.90  
  7 purchase totals = $1,319.73       $1,441.4492   $1,441.45   $1,441.40   $1,441.50