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	$241.43	5.428%	$254.5348	$254.53	$254.55	$254.50
Purchase #2	$137.30	7.443%	$147.5192	$147.52	$147.50	$147.50
Purchase #3	$55.99	5.504%	$59.0717	$59.07	$59.05	$59.10
Purchase #4	$162.57	10.672%	$179.9195	$179.92	$179.90	$179.90
Purchase #5	$173.98	7.803%	$187.5557	$187.56	$187.55	$187.60
Purchase #6	$159.93	8.370%	$173.3161	$173.32	$173.30	$173.30
Purchase #7	$235.70	6.227%	$250.377	$250.38	$250.40	$250.40
7 purchase totals =	$1,166.90		$1,252.2940	$1,252.30	$1,252.25	$1,252.30