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	$44.59	4.462%	$46.5796	$46.58	$46.60	$46.60
Purchase #2	$45.50	4.200%	$47.411	$47.41	$47.40	$47.40
Purchase #3	$250.63	6.615%	$267.2092	$267.21	$267.20	$267.20
Purchase #4	$178.93	6.766%	$191.0364	$191.04	$191.05	$191.00
Purchase #5	$48.88	13.136%	$55.3009	$55.30	$55.30	$55.30
Purchase #6	$140.80	10.195%	$155.1546	$155.15	$155.15	$155.20
Purchase #7	$228.84	10.849%	$253.6669	$253.67	$253.65	$253.70
7 purchase totals =	$938.17		$1,016.3586	$1,016.36	$1,016.35	$1,016.40