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	$158.64	8.139%	$171.5517	$171.55	$171.55	$171.60
Purchase #2	$108.84	10.700%	$120.4859	$120.49	$120.50	$120.50
Purchase #3	$222.78	5.229%	$234.4292	$234.43	$234.45	$234.40
Purchase #4	$144.77	7.423%	$155.5163	$155.52	$155.50	$155.50
Purchase #5	$81.55	11.541%	$90.9617	$90.96	$90.95	$91.00
Purchase #6	$45.87	5.146%	$48.2305	$48.23	$48.25	$48.20
Purchase #7	$40.47	3.786%	$42.0022	$42.00	$42.00	$42.00
7 purchase totals =	$802.92		$863.1775	$863.18	$863.20	$863.20