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	$42.42	4.415%	$44.2928	$44.29	$44.30	$44.30
Purchase #2	$223.73	11.143%	$248.6602	$248.66	$248.65	$248.70
Purchase #3	$85.47	5.132%	$89.8563	$89.86	$89.85	$89.90
Purchase #4	$19.49	4.532%	$20.3733	$20.37	$20.35	$20.40
Purchase #5	$10.61	5.721%	$11.217	$11.22	$11.20	$11.20
Purchase #6	$250.45	10.514%	$276.7823	$276.78	$276.80	$276.80
Purchase #7	$62.68	3.608%	$64.9415	$64.94	$64.95	$64.90
7 purchase totals =	$694.85		$756.1234	$756.12	$756.10	$756.20