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	$15.50	11.745%	$17.3205	$17.32	$17.30	$17.30
Purchase #2	$115.93	6.717%	$123.717	$123.72	$123.70	$123.70
Purchase #3	$221.28	6.122%	$234.8268	$234.83	$234.85	$234.80
Purchase #4	$94.36	5.511%	$99.5602	$99.56	$99.55	$99.60
Purchase #5	$158.58	9.293%	$173.3168	$173.32	$173.30	$173.30
Purchase #6	$240.52	3.215%	$248.2527	$248.25	$248.25	$248.30
Purchase #7	$146.27	3.759%	$151.7683	$151.77	$151.75	$151.80
7 purchase totals =	$992.44		$1,048.7623	$1,048.77	$1,048.70	$1,048.80