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	$101.88	3.362%	$105.3052	$105.31	$105.30	$105.30
Purchase #2	$66.49	5.208%	$69.9528	$69.95	$69.95	$70.00
Purchase #3	$105.52	8.749%	$114.7519	$114.75	$114.75	$114.80
Purchase #4	$70.41	8.726%	$76.554	$76.55	$76.55	$76.60
Purchase #5	$190.25	3.251%	$196.435	$196.44	$196.45	$196.40
Purchase #6	$165.84	4.270%	$172.9214	$172.92	$172.90	$172.90
Purchase #7	$248.86	11.548%	$277.5984	$277.60	$277.60	$277.60
7 purchase totals =	$949.25		$1,013.5187	$1,013.52	$1,013.50	$1,013.60