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 $176.71   11.831%   $197.6166   $197.62   $197.60   $197.60  
  Purchase #2 $79.38   9.423%   $86.86   $86.86   $86.85   $86.90  
  Purchase #3 $99.91   4.111%   $104.0173   $104.02   $104.00   $104.00  
  Purchase #4 $83.37   3.355%   $86.1671   $86.17   $86.15   $86.20  
  Purchase #5 $245.86   12.592%   $276.8187   $276.82   $276.80   $276.80  
  Purchase #6 $208.83   9.110%   $227.8544   $227.85   $227.85   $227.90  
  Purchase #7 $85.84   11.515%   $95.7245   $95.72   $95.70   $95.70  
  7 purchase totals = $979.90       $1,075.0586   $1,075.06   $1,074.95   $1,075.10