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	$169.50	10.531%	$187.35	$187.35	$187.35	$187.40
Purchase #2	$54.52	12.293%	$61.2221	$61.22	$61.20	$61.20
Purchase #3	$10.99	7.632%	$11.8288	$11.83	$11.85	$11.80
Purchase #4	$163.44	7.333%	$175.4251	$175.43	$175.45	$175.40
Purchase #5	$48.56	10.427%	$53.6234	$53.62	$53.60	$53.60
Purchase #6	$204.37	5.147%	$214.8889	$214.89	$214.90	$214.90
Purchase #7	$172.89	3.433%	$178.8253	$178.83	$178.85	$178.80
7 purchase totals =	$824.27		$883.1636	$883.17	$883.20	$883.10