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	$38.51	11.476%	$42.9294	$42.93	$42.95	$42.90
Purchase #2	$10.33	12.217%	$11.592	$11.59	$11.60	$11.60
Purchase #3	$102.92	8.388%	$111.5529	$111.55	$111.55	$111.60
Purchase #4	$209.27	7.861%	$225.7207	$225.72	$225.70	$225.70
Purchase #5	$174.83	5.572%	$184.5715	$184.57	$184.55	$184.60
Purchase #6	$202.34	7.257%	$217.0238	$217.02	$217.00	$217.00
Purchase #7	$34.64	13.608%	$39.3538	$39.35	$39.35	$39.40
7 purchase totals =	$772.84		$832.7441	$832.73	$832.70	$832.80