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 $159.47   9.555%   $174.7074   $174.71   $174.70   $174.70  
  Purchase #2 $225.63   5.149%   $237.2477   $237.25   $237.25   $237.20  
  Purchase #3 $147.80   7.512%   $158.9027   $158.90   $158.90   $158.90  
  Purchase #4 $44.74   4.696%   $46.841   $46.84   $46.85   $46.80  
  Purchase #5 $141.32   7.620%   $152.0886   $152.09   $152.10   $152.10  
  Purchase #6 $163.76   9.553%   $179.404   $179.40   $179.40   $179.40  
  Purchase #7 $205.88   10.328%   $227.1433   $227.14   $227.15   $227.10  
  7 purchase totals = $1,088.60       $1,176.3347   $1,176.33   $1,176.35   $1,176.20