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	$62.68	7.158%	$67.1666	$67.17	$67.15	$67.20
Purchase #2	$64.94	9.644%	$71.2028	$71.20	$71.20	$71.20
Purchase #3	$207.62	4.123%	$216.1802	$216.18	$216.20	$216.20
Purchase #4	$193.77	3.278%	$200.1218	$200.12	$200.10	$200.10
Purchase #5	$200.31	13.116%	$226.5827	$226.58	$226.60	$226.60
Purchase #6	$92.40	8.760%	$100.4942	$100.49	$100.50	$100.50
Purchase #7	$126.36	3.308%	$130.54	$130.54	$130.55	$130.50
7 purchase totals =	$948.08		$1,012.2883	$1,012.28	$1,012.30	$1,012.30