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	$97.65	13.690%	$111.0183	$111.02	$111.00	$111.00
Purchase #2	$88.29	5.226%	$92.904	$92.90	$92.90	$92.90
Purchase #3	$56.80	10.456%	$62.739	$62.74	$62.75	$62.70
Purchase #4	$172.45	4.268%	$179.8102	$179.81	$179.80	$179.80
Purchase #5	$240.63	4.325%	$251.0372	$251.04	$251.05	$251.00
Purchase #6	$142.59	5.418%	$150.3155	$150.32	$150.30	$150.30
Purchase #7	$122.64	4.177%	$127.7627	$127.76	$127.75	$127.80
7 purchase totals =	$921.05		$975.5869	$975.59	$975.55	$975.50