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	$244.61	8.463%	$265.3113	$265.31	$265.30	$265.30
Purchase #2	$181.65	3.171%	$187.4101	$187.41	$187.40	$187.40
Purchase #3	$182.80	6.181%	$194.0989	$194.10	$194.10	$194.10
Purchase #4	$78.57	13.788%	$89.4032	$89.40	$89.40	$89.40
Purchase #5	$151.63	12.526%	$170.6232	$170.62	$170.60	$170.60
Purchase #6	$140.25	4.852%	$147.0549	$147.05	$147.05	$147.10
Purchase #7	$139.88	13.302%	$158.4868	$158.49	$158.50	$158.50
7 purchase totals =	$1,119.39		$1,212.3884	$1,212.38	$1,212.35	$1,212.40