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	$8.80	9.734%	$9.6566	$9.66	$9.65	$9.70
Purchase #2	$40.61	12.324%	$45.6148	$45.61	$45.60	$45.60
Purchase #3	$37.28	11.440%	$41.5448	$41.54	$41.55	$41.50
Purchase #4	$109.80	13.682%	$124.8228	$124.82	$124.80	$124.80
Purchase #5	$158.69	6.710%	$169.3381	$169.34	$169.35	$169.30
Purchase #6	$139.62	4.799%	$146.3204	$146.32	$146.30	$146.30
Purchase #7	$152.92	13.152%	$173.032	$173.03	$173.05	$173.00
7 purchase totals =	$647.72		$710.3295	$710.32	$710.30	$710.20