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 $166.32   4.851%   $174.3882   $174.39   $174.40   $174.40  
  Purchase #2 $229.90   11.327%   $255.9408   $255.94   $255.95   $255.90  
  Purchase #3 $21.75   11.515%   $24.2545   $24.25   $24.25   $24.30  
  Purchase #4 $179.59   11.209%   $199.7202   $199.72   $199.70   $199.70  
  Purchase #5 $170.44   12.416%   $191.6018   $191.60   $191.60   $191.60  
  Purchase #6 $189.92   7.856%   $204.8401   $204.84   $204.85   $204.80  
  Purchase #7 $168.62   4.549%   $176.2905   $176.29   $176.30   $176.30  
  7 purchase totals = $1,126.54       $1,227.0361   $1,227.03   $1,227.05   $1,227.00