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 $44.96   7.520%   $48.341   $48.34   $48.35   $48.30  
  Purchase #2 $176.96   8.747%   $192.4387   $192.44   $192.45   $192.40  
  Purchase #3 $148.99   7.449%   $160.0883   $160.09   $160.10   $160.10  
  Purchase #4 $245.84   5.556%   $259.4989   $259.50   $259.50   $259.50  
  Purchase #5 $76.70   7.167%   $82.1971   $82.20   $82.20   $82.20  
  Purchase #6 $88.91   5.293%   $93.616   $93.62   $93.60   $93.60  
  Purchase #7 $138.88   8.867%   $151.1945   $151.19   $151.20   $151.20  
  7 purchase totals = $921.24       $987.3745   $987.38   $987.40   $987.30