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	$154.59	12.323%	$173.6401	$173.64	$173.65	$173.60
Purchase #2	$54.32	9.111%	$59.2691	$59.27	$59.25	$59.30
Purchase #3	$147.73	11.563%	$164.812	$164.81	$164.80	$164.80
Purchase #4	$241.58	4.333%	$252.0477	$252.05	$252.05	$252.00
Purchase #5	$64.30	7.420%	$69.0711	$69.07	$69.05	$69.10
Purchase #6	$223.32	3.578%	$231.3104	$231.31	$231.30	$231.30
Purchase #7	$228.29	5.621%	$241.1222	$241.12	$241.10	$241.10
7 purchase totals =	$1,114.13		$1,191.2726	$1,191.27	$1,191.20	$1,191.20