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	$228.98	10.190%	$252.3131	$252.31	$252.30	$252.30
Purchase #2	$102.68	6.809%	$109.6715	$109.67	$109.65	$109.70
Purchase #3	$220.74	9.693%	$242.1363	$242.14	$242.15	$242.10
Purchase #4	$31.34	8.588%	$34.0315	$34.03	$34.05	$34.00
Purchase #5	$146.90	10.635%	$162.5228	$162.52	$162.50	$162.50
Purchase #6	$167.45	3.168%	$172.7548	$172.75	$172.75	$172.80
Purchase #7	$82.39	9.758%	$90.4296	$90.43	$90.45	$90.40
7 purchase totals =	$980.48		$1,063.8596	$1,063.85	$1,063.85	$1,063.80