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	$50.82	10.802%	$56.3096	$56.31	$56.30	$56.30
Purchase #2	$250.28	8.119%	$270.6002	$270.60	$270.60	$270.60
Purchase #3	$242.75	13.596%	$275.7543	$275.75	$275.75	$275.80
Purchase #4	$50.88	4.849%	$53.3472	$53.35	$53.35	$53.30
Purchase #5	$172.84	13.539%	$196.2408	$196.24	$196.25	$196.20
Purchase #6	$40.49	11.769%	$45.2553	$45.26	$45.25	$45.30
Purchase #7	$153.94	3.263%	$158.9631	$158.96	$158.95	$159.00
7 purchase totals =	$962.00		$1,056.4705	$1,056.47	$1,056.45	$1,056.50