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 $69.74   9.830%   $76.5954   $76.60   $76.60   $76.60  
  Purchase #2 $94.39   8.408%   $102.3263   $102.33   $102.35   $102.30  
  Purchase #3 $222.59   5.449%   $234.7189   $234.72   $234.70   $234.70  
  Purchase #4 $124.79   10.807%   $138.2761   $138.28   $138.30   $138.30  
  Purchase #5 $185.99   3.868%   $193.1841   $193.18   $193.20   $193.20  
  Purchase #6 $108.79   4.730%   $113.9358   $113.94   $113.95   $113.90  
  Purchase #7 $250.61   4.467%   $261.8047   $261.80   $261.80   $261.80  
  7 purchase totals = $1,056.90       $1,120.8413   $1,120.85   $1,120.90   $1,120.80