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	$107.89	3.540%	$111.7093	$111.71	$111.70	$111.70
Purchase #2	$232.77	10.236%	$256.5963	$256.60	$256.60	$256.60
Purchase #3	$250.98	6.488%	$267.2636	$267.26	$267.25	$267.30
Purchase #4	$78.63	10.291%	$86.7218	$86.72	$86.70	$86.70
Purchase #5	$67.55	3.204%	$69.7143	$69.71	$69.70	$69.70
Purchase #6	$214.50	12.549%	$241.4176	$241.42	$241.40	$241.40
Purchase #7	$151.29	7.733%	$162.9893	$162.99	$163.00	$163.00
7 purchase totals =	$1,103.61		$1,196.4122	$1,196.41	$1,196.35	$1,196.40