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	$59.71	9.723%	$65.5156	$65.52	$65.50	$65.50
Purchase #2	$146.27	13.763%	$166.4011	$166.40	$166.40	$166.40
Purchase #3	$162.45	5.550%	$171.466	$171.47	$171.45	$171.50
Purchase #4	$161.77	6.714%	$172.6312	$172.63	$172.65	$172.60
Purchase #5	$153.92	8.296%	$166.6892	$166.69	$166.70	$166.70
Purchase #6	$30.68	8.678%	$33.3424	$33.34	$33.35	$33.30
Purchase #7	$113.63	4.436%	$118.6706	$118.67	$118.65	$118.70
7 purchase totals =	$828.43		$894.7161	$894.72	$894.70	$894.70