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	$153.59	12.595%	$172.9347	$172.93	$172.95	$172.90
Purchase #2	$173.46	4.117%	$180.6013	$180.60	$180.60	$180.60
Purchase #3	$75.73	3.403%	$78.3071	$78.31	$78.30	$78.30
Purchase #4	$105.71	8.171%	$114.3476	$114.35	$114.35	$114.30
Purchase #5	$17.75	3.838%	$18.4312	$18.43	$18.45	$18.40
Purchase #6	$43.51	12.227%	$48.83	$48.83	$48.85	$48.80
Purchase #7	$155.87	3.860%	$161.8866	$161.89	$161.90	$161.90
7 purchase totals =	$725.62		$775.3385	$775.34	$775.40	$775.20