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	$152.90	13.793%	$173.9895	$173.99	$174.00	$174.00
Purchase #2	$16.29	11.796%	$18.2116	$18.21	$18.20	$18.20
Purchase #3	$114.77	11.415%	$127.871	$127.87	$127.85	$127.90
Purchase #4	$119.58	6.410%	$127.2451	$127.25	$127.25	$127.20
Purchase #5	$135.77	12.156%	$152.2742	$152.27	$152.25	$152.30
Purchase #6	$226.78	9.863%	$249.1473	$249.15	$249.15	$249.10
Purchase #7	$119.54	10.217%	$131.7534	$131.75	$131.75	$131.80
7 purchase totals =	$885.63		$980.4921	$980.49	$980.45	$980.50