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	$54.65	12.772%	$61.6299	$61.63	$61.65	$61.60
Purchase #2	$153.30	12.520%	$172.4932	$172.49	$172.50	$172.50
Purchase #3	$102.74	8.121%	$111.0835	$111.08	$111.10	$111.10
Purchase #4	$201.41	10.719%	$222.9991	$223.00	$223.00	$223.00
Purchase #5	$166.50	4.387%	$173.8044	$173.80	$173.80	$173.80
Purchase #6	$119.92	6.410%	$127.6069	$127.61	$127.60	$127.60
Purchase #7	$127.26	3.517%	$131.7357	$131.74	$131.75	$131.70
7 purchase totals =	$925.78		$1,001.3527	$1,001.35	$1,001.40	$1,001.30