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	$225.32	5.797%	$238.3818	$238.38	$238.40	$238.40
Purchase #2	$111.48	5.451%	$117.5568	$117.56	$117.55	$117.60
Purchase #3	$142.42	3.388%	$147.2452	$147.25	$147.25	$147.20
Purchase #4	$151.54	8.636%	$164.627	$164.63	$164.65	$164.60
Purchase #5	$70.67	11.346%	$78.6882	$78.69	$78.70	$78.70
Purchase #6	$244.52	12.321%	$274.6473	$274.65	$274.65	$274.60
Purchase #7	$139.70	10.406%	$154.2372	$154.24	$154.25	$154.20
7 purchase totals =	$1,085.65		$1,175.3835	$1,175.40	$1,175.45	$1,175.30