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	$107.39	3.212%	$110.8394	$110.84	$110.85	$110.80
Purchase #2	$15.74	5.512%	$16.6076	$16.61	$16.60	$16.60
Purchase #3	$84.72	5.512%	$89.3898	$89.39	$89.40	$89.40
Purchase #4	$9.67	12.532%	$10.8818	$10.88	$10.90	$10.90
Purchase #5	$103.99	7.594%	$111.887	$111.89	$111.90	$111.90
Purchase #6	$236.69	12.463%	$266.1887	$266.19	$266.20	$266.20
Purchase #7	$78.80	13.119%	$89.1378	$89.14	$89.15	$89.10
7 purchase totals =	$637.00		$694.9321	$694.94	$695.00	$694.90