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	$48.82	9.846%	$53.6268	$53.63	$53.65	$53.60
Purchase #2	$33.58	3.167%	$34.6435	$34.64	$34.65	$34.60
Purchase #3	$228.93	5.537%	$241.6059	$241.61	$241.60	$241.60
Purchase #4	$125.75	4.350%	$131.2201	$131.22	$131.20	$131.20
Purchase #5	$46.99	9.700%	$51.548	$51.55	$51.55	$51.50
Purchase #6	$223.82	6.672%	$238.7533	$238.75	$238.75	$238.80
Purchase #7	$45.63	12.261%	$51.2247	$51.22	$51.20	$51.20
7 purchase totals =	$753.52		$802.6223	$802.62	$802.60	$802.50