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	$100.92	4.368%	$105.3282	$105.33	$105.35	$105.30
Purchase #2	$42.59	6.393%	$45.3128	$45.31	$45.30	$45.30
Purchase #3	$77.62	10.295%	$85.611	$85.61	$85.60	$85.60
Purchase #4	$44.32	5.528%	$46.77	$46.77	$46.75	$46.80
Purchase #5	$107.80	8.557%	$117.0244	$117.02	$117.00	$117.00
Purchase #6	$57.44	12.773%	$64.7768	$64.78	$64.80	$64.80
Purchase #7	$48.34	12.576%	$54.4192	$54.42	$54.40	$54.40
7 purchase totals =	$479.03		$519.2424	$519.24	$519.20	$519.20