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 $169.85   3.617%   $175.9935   $175.99   $176.00   $176.00  
  Purchase #2 $241.60   10.831%   $267.7677   $267.77   $267.75   $267.80  
  Purchase #3 $21.61   12.670%   $24.348   $24.35   $24.35   $24.30  
  Purchase #4 $118.93   7.862%   $128.2803   $128.28   $128.30   $128.30  
  Purchase #5 $167.38   9.443%   $183.1857   $183.19   $183.20   $183.20  
  Purchase #6 $231.60   8.636%   $251.601   $251.60   $251.60   $251.60  
  Purchase #7 $161.60   6.825%   $172.6292   $172.63   $172.65   $172.60  
  7 purchase totals = $1,112.57       $1,203.8054   $1,203.81   $1,203.85   $1,203.80