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	$231.84	9.853%	$254.6832	$254.68	$254.70	$254.70
Purchase #2	$9.29	13.654%	$10.5585	$10.56	$10.55	$10.60
Purchase #3	$155.70	6.795%	$166.2798	$166.28	$166.30	$166.30
Purchase #4	$152.65	13.114%	$172.6685	$172.67	$172.65	$172.70
Purchase #5	$233.61	3.111%	$240.8776	$240.88	$240.90	$240.90
Purchase #6	$150.34	13.503%	$170.6404	$170.64	$170.65	$170.60
Purchase #7	$123.32	9.332%	$134.8282	$134.83	$134.85	$134.80
7 purchase totals =	$1,056.75		$1,150.5362	$1,150.54	$1,150.60	$1,150.60