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	$105.50	4.433%	$110.1768	$110.18	$110.20	$110.20
Purchase #2	$162.61	6.748%	$173.5829	$173.58	$173.60	$173.60
Purchase #3	$209.36	11.536%	$233.5118	$233.51	$233.50	$233.50
Purchase #4	$31.88	5.433%	$33.612	$33.61	$33.60	$33.60
Purchase #5	$151.78	4.648%	$158.8347	$158.83	$158.85	$158.80
Purchase #6	$213.77	7.844%	$230.5381	$230.54	$230.55	$230.50
Purchase #7	$210.39	6.840%	$224.7807	$224.78	$224.80	$224.80
7 purchase totals =	$1,085.29		$1,165.0370	$1,165.03	$1,165.10	$1,165.00