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	$198.55	6.687%	$211.827	$211.83	$211.85	$211.80
Purchase #2	$15.59	11.552%	$17.391	$17.39	$17.40	$17.40
Purchase #3	$98.43	13.294%	$111.5153	$111.52	$111.50	$111.50
Purchase #4	$248.60	8.747%	$270.345	$270.35	$270.35	$270.30
Purchase #5	$9.56	6.512%	$10.1825	$10.18	$10.20	$10.20
Purchase #6	$62.58	11.141%	$69.552	$69.55	$69.55	$69.60
Purchase #7	$233.72	13.712%	$265.7677	$265.77	$265.75	$265.80
7 purchase totals =	$867.03		$956.5805	$956.59	$956.60	$956.60