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	$151.68	13.383%	$171.9793	$171.98	$172.00	$172.00
Purchase #2	$233.91	11.398%	$260.5711	$260.57	$260.55	$260.60
Purchase #3	$105.37	5.556%	$111.2244	$111.22	$111.20	$111.20
Purchase #4	$38.91	7.489%	$41.824	$41.82	$41.80	$41.80
Purchase #5	$200.51	4.545%	$209.6232	$209.62	$209.60	$209.60
Purchase #6	$152.61	8.378%	$165.3957	$165.40	$165.40	$165.40
Purchase #7	$74.92	13.818%	$85.2724	$85.27	$85.25	$85.30
7 purchase totals =	$957.91		$1,045.8901	$1,045.88	$1,045.80	$1,045.90