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	$208.52	7.598%	$224.3633	$224.36	$224.35	$224.40
Purchase #2	$170.81	13.661%	$194.1444	$194.14	$194.15	$194.10
Purchase #3	$222.97	4.643%	$233.3225	$233.32	$233.30	$233.30
Purchase #4	$65.86	10.148%	$72.5435	$72.54	$72.55	$72.50
Purchase #5	$118.50	9.294%	$129.5134	$129.51	$129.50	$129.50
Purchase #6	$231.33	10.371%	$255.3212	$255.32	$255.30	$255.30
Purchase #7	$24.28	10.678%	$26.8726	$26.87	$26.85	$26.90
7 purchase totals =	$1,042.27		$1,136.0809	$1,136.06	$1,136.00	$1,136.00