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	$141.54	3.402%	$146.3552	$146.36	$146.35	$146.40
Purchase #2	$63.88	13.255%	$72.3473	$72.35	$72.35	$72.30
Purchase #3	$52.45	5.651%	$55.4139	$55.41	$55.40	$55.40
Purchase #4	$158.50	12.463%	$178.2539	$178.25	$178.25	$178.30
Purchase #5	$165.91	4.516%	$173.4025	$173.40	$173.40	$173.40
Purchase #6	$76.59	13.178%	$86.683	$86.68	$86.70	$86.70
Purchase #7	$19.62	3.170%	$20.242	$20.24	$20.25	$20.20
7 purchase totals =	$678.49		$732.6978	$732.69	$732.70	$732.70