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	$148.52	6.526%	$158.2124	$158.21	$158.20	$158.20
Purchase #2	$58.64	4.539%	$61.3017	$61.30	$61.30	$61.30
Purchase #3	$21.65	9.660%	$23.7414	$23.74	$23.75	$23.70
Purchase #4	$50.79	3.562%	$52.5991	$52.60	$52.60	$52.60
Purchase #5	$115.89	9.776%	$127.2194	$127.22	$127.20	$127.20
Purchase #6	$218.43	13.808%	$248.5908	$248.59	$248.60	$248.60
Purchase #7	$98.87	10.538%	$109.2889	$109.29	$109.30	$109.30
7 purchase totals =	$712.79		$780.9537	$780.95	$780.95	$780.90