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	$184.40	11.127%	$204.9182	$204.92	$204.90	$204.90
Purchase #2	$178.31	3.736%	$184.9717	$184.97	$184.95	$185.00
Purchase #3	$52.91	11.872%	$59.1915	$59.19	$59.20	$59.20
Purchase #4	$228.87	4.559%	$239.3042	$239.30	$239.30	$239.30
Purchase #5	$48.80	8.801%	$53.0949	$53.09	$53.10	$53.10
Purchase #6	$105.25	11.615%	$117.4748	$117.47	$117.45	$117.50
Purchase #7	$138.50	10.672%	$153.2807	$153.28	$153.30	$153.30
7 purchase totals =	$937.04		$1,012.2360	$1,012.22	$1,012.20	$1,012.30