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	$166.56	3.353%	$172.1448	$172.14	$172.15	$172.10
Purchase #2	$116.30	6.182%	$123.4897	$123.49	$123.50	$123.50
Purchase #3	$141.95	11.434%	$158.1806	$158.18	$158.20	$158.20
Purchase #4	$119.38	9.789%	$131.0661	$131.07	$131.05	$131.10
Purchase #5	$132.31	3.730%	$137.2452	$137.25	$137.25	$137.20
Purchase #6	$173.58	13.308%	$196.68	$196.68	$196.70	$196.70
Purchase #7	$88.98	7.391%	$95.5565	$95.56	$95.55	$95.60
7 purchase totals =	$939.06		$1,014.3629	$1,014.37	$1,014.40	$1,014.40