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	$184.32	11.717%	$205.9168	$205.92	$205.90	$205.90
Purchase #2	$147.75	7.565%	$158.9273	$158.93	$158.95	$158.90
Purchase #3	$91.74	12.610%	$103.3084	$103.31	$103.30	$103.30
Purchase #4	$168.99	8.474%	$183.3102	$183.31	$183.30	$183.30
Purchase #5	$230.98	4.770%	$241.9977	$242.00	$242.00	$242.00
Purchase #6	$174.71	12.696%	$196.8912	$196.89	$196.90	$196.90
Purchase #7	$111.77	6.120%	$118.6103	$118.61	$118.60	$118.60
7 purchase totals =	$1,110.26		$1,208.9619	$1,208.97	$1,208.95	$1,208.90