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	$15.73	3.482%	$16.2777	$16.28	$16.30	$16.30
Purchase #2	$169.74	3.458%	$175.6096	$175.61	$175.60	$175.60
Purchase #3	$52.73	12.130%	$59.1261	$59.13	$59.15	$59.10
Purchase #4	$35.86	3.810%	$37.2263	$37.23	$37.25	$37.20
Purchase #5	$51.99	11.595%	$58.0182	$58.02	$58.00	$58.00
Purchase #6	$39.85	13.387%	$45.1847	$45.18	$45.20	$45.20
Purchase #7	$34.54	9.131%	$37.6938	$37.69	$37.70	$37.70
7 purchase totals =	$400.44		$429.1364	$429.14	$429.20	$429.10