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	$95.40	8.408%	$103.4212	$103.42	$103.40	$103.40
Purchase #2	$110.32	7.408%	$118.4925	$118.49	$118.50	$118.50
Purchase #3	$210.62	12.731%	$237.434	$237.43	$237.45	$237.40
Purchase #4	$44.28	6.162%	$47.0085	$47.01	$47.00	$47.00
Purchase #5	$134.83	10.171%	$148.5436	$148.54	$148.55	$148.50
Purchase #6	$113.47	12.181%	$127.2918	$127.29	$127.30	$127.30
Purchase #7	$124.58	10.123%	$137.1912	$137.19	$137.20	$137.20
7 purchase totals =	$833.50		$919.3828	$919.37	$919.40	$919.30