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	$165.63	11.105%	$184.0232	$184.02	$184.00	$184.00
Purchase #2	$224.85	13.217%	$254.5684	$254.57	$254.55	$254.60
Purchase #3	$11.41	7.181%	$12.2294	$12.23	$12.25	$12.20
Purchase #4	$5.96	13.687%	$6.7757	$6.78	$6.80	$6.80
Purchase #5	$173.32	10.425%	$191.3886	$191.39	$191.40	$191.40
Purchase #6	$127.43	9.570%	$139.6251	$139.63	$139.65	$139.60
Purchase #7	$174.77	8.617%	$189.8299	$189.83	$189.85	$189.80
7 purchase totals =	$883.37		$978.4403	$978.45	$978.50	$978.40