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	$149.25	6.361%	$158.7438	$158.74	$158.75	$158.70
Purchase #2	$131.43	10.541%	$145.284	$145.28	$145.30	$145.30
Purchase #3	$121.74	4.641%	$127.39	$127.39	$127.40	$127.40
Purchase #4	$76.92	3.472%	$79.5907	$79.59	$79.60	$79.60
Purchase #5	$122.45	7.710%	$131.8909	$131.89	$131.90	$131.90
Purchase #6	$48.60	11.403%	$54.1419	$54.14	$54.15	$54.10
Purchase #7	$44.27	9.430%	$48.4447	$48.44	$48.45	$48.40
7 purchase totals =	$694.66		$745.4860	$745.47	$745.55	$745.40