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	$152.94	10.418%	$168.8733	$168.87	$168.85	$168.90
Purchase #2	$47.91	7.524%	$51.5147	$51.51	$51.50	$51.50
Purchase #3	$209.96	13.323%	$237.933	$237.93	$237.95	$237.90
Purchase #4	$222.39	12.135%	$249.377	$249.38	$249.40	$249.40
Purchase #5	$96.68	13.579%	$109.8082	$109.81	$109.80	$109.80
Purchase #6	$164.68	4.751%	$172.5039	$172.50	$172.50	$172.50
Purchase #7	$241.87	13.242%	$273.8984	$273.90	$273.90	$273.90
7 purchase totals =	$1,136.43		$1,263.9085	$1,263.90	$1,263.90	$1,263.90