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	$110.52	7.308%	$118.5968	$118.60	$118.60	$118.60
Purchase #2	$196.57	9.504%	$215.252	$215.25	$215.25	$215.30
Purchase #3	$156.81	6.782%	$167.4449	$167.44	$167.45	$167.40
Purchase #4	$172.38	5.355%	$181.6109	$181.61	$181.60	$181.60
Purchase #5	$181.82	13.170%	$205.7657	$205.77	$205.75	$205.80
Purchase #6	$51.31	6.191%	$54.4866	$54.49	$54.50	$54.50
Purchase #7	$196.45	4.335%	$204.9661	$204.97	$204.95	$205.00
7 purchase totals =	$1,065.86		$1,148.1230	$1,148.13	$1,148.10	$1,148.20