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	$173.92	10.298%	$191.8303	$191.83	$191.85	$191.80
Purchase #2	$138.83	11.636%	$154.9843	$154.98	$155.00	$155.00
Purchase #3	$49.41	3.755%	$51.2653	$51.27	$51.25	$51.30
Purchase #4	$229.34	4.771%	$240.2818	$240.28	$240.30	$240.30
Purchase #5	$136.28	7.136%	$146.0049	$146.00	$146.00	$146.00
Purchase #6	$99.57	11.853%	$111.372	$111.37	$111.35	$111.40
Purchase #7	$86.84	5.674%	$91.7673	$91.77	$91.75	$91.80
7 purchase totals =	$914.19		$987.5059	$987.50	$987.50	$987.60