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	$54.28	9.461%	$59.4154	$59.42	$59.40	$59.40
Purchase #2	$97.95	7.706%	$105.498	$105.50	$105.50	$105.50
Purchase #3	$152.48	13.346%	$172.83	$172.83	$172.85	$172.80
Purchase #4	$212.95	7.251%	$228.391	$228.39	$228.40	$228.40
Purchase #5	$23.28	5.739%	$24.616	$24.62	$24.60	$24.60
Purchase #6	$241.53	10.821%	$267.666	$267.67	$267.65	$267.70
Purchase #7	$83.93	11.798%	$93.8321	$93.83	$93.85	$93.80
7 purchase totals =	$866.40		$952.2485	$952.26	$952.25	$952.20