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	$204.54	7.409%	$219.6944	$219.69	$219.70	$219.70
Purchase #2	$51.73	5.756%	$54.7076	$54.71	$54.70	$54.70
Purchase #3	$121.75	4.743%	$127.5246	$127.52	$127.50	$127.50
Purchase #4	$45.75	7.401%	$49.136	$49.14	$49.15	$49.10
Purchase #5	$229.71	6.239%	$244.0416	$244.04	$244.05	$244.00
Purchase #6	$61.59	3.385%	$63.6748	$63.67	$63.65	$63.70
Purchase #7	$39.32	8.406%	$42.6252	$42.63	$42.65	$42.60
7 purchase totals =	$754.39		$801.4042	$801.40	$801.40	$801.30