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	$208.92	7.495%	$224.5786	$224.58	$224.60	$224.60
Purchase #2	$59.73	11.230%	$66.4377	$66.44	$66.45	$66.40
Purchase #3	$96.89	8.616%	$105.238	$105.24	$105.25	$105.20
Purchase #4	$175.85	6.406%	$187.115	$187.12	$187.10	$187.10
Purchase #5	$26.30	4.660%	$27.5256	$27.53	$27.55	$27.50
Purchase #6	$38.48	10.823%	$42.6447	$42.64	$42.65	$42.60
Purchase #7	$78.48	12.262%	$88.1032	$88.10	$88.10	$88.10
7 purchase totals =	$684.65		$741.6428	$741.65	$741.70	$741.50