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	$56.34	11.759%	$62.965	$62.97	$62.95	$63.00
Purchase #2	$237.96	7.470%	$255.7356	$255.74	$255.75	$255.70
Purchase #3	$85.92	4.742%	$89.9943	$89.99	$90.00	$90.00
Purchase #4	$132.35	11.513%	$147.5875	$147.59	$147.60	$147.60
Purchase #5	$71.62	13.828%	$81.5236	$81.52	$81.50	$81.50
Purchase #6	$151.87	4.296%	$158.3943	$158.39	$158.40	$158.40
Purchase #7	$13.85	8.499%	$15.0271	$15.03	$15.05	$15.00
7 purchase totals =	$749.91		$811.2274	$811.23	$811.25	$811.20