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	$12.89	13.724%	$14.659	$14.66	$14.65	$14.70
Purchase #2	$38.37	4.374%	$40.0483	$40.05	$40.05	$40.00
Purchase #3	$26.65	9.870%	$29.2804	$29.28	$29.30	$29.30
Purchase #4	$78.73	4.250%	$82.076	$82.08	$82.10	$82.10
Purchase #5	$158.35	5.734%	$167.4298	$167.43	$167.45	$167.40
Purchase #6	$10.89	9.191%	$11.8909	$11.89	$11.90	$11.90
Purchase #7	$54.91	5.357%	$57.8515	$57.85	$57.85	$57.90
7 purchase totals =	$380.79		$403.2359	$403.24	$403.30	$403.30