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 $222.82   8.599%   $241.9803   $241.98   $242.00   $242.00  
  Purchase #2 $168.73   4.752%   $176.748   $176.75   $176.75   $176.70  
  Purchase #3 $79.62   4.643%   $83.3168   $83.32   $83.30   $83.30  
  Purchase #4 $170.56   4.117%   $177.582   $177.58   $177.60   $177.60  
  Purchase #5 $152.61   5.599%   $161.1546   $161.15   $161.15   $161.20  
  Purchase #6 $225.26   4.723%   $235.899   $235.90   $235.90   $235.90  
  Purchase #7 $64.77   9.423%   $70.8733   $70.87   $70.85   $70.90  
  7 purchase totals = $1,084.37       $1,147.5540   $1,147.55   $1,147.55   $1,147.60