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	$67.43	6.178%	$71.5958	$71.60	$71.60	$71.60
Purchase #2	$114.37	4.268%	$119.2513	$119.25	$119.25	$119.30
Purchase #3	$107.50	3.805%	$111.5904	$111.59	$111.60	$111.60
Purchase #4	$111.82	11.713%	$124.9175	$124.92	$124.90	$124.90
Purchase #5	$49.79	6.565%	$53.0587	$53.06	$53.05	$53.10
Purchase #6	$116.65	9.174%	$127.3515	$127.35	$127.35	$127.40
Purchase #7	$28.42	6.751%	$30.3386	$30.34	$30.35	$30.30
7 purchase totals =	$595.98		$638.1038	$638.11	$638.10	$638.20