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	$70.92	4.489%	$74.1036	$74.10	$74.10	$74.10
Purchase #2	$63.92	3.243%	$65.9929	$65.99	$66.00	$66.00
Purchase #3	$243.72	6.513%	$259.5935	$259.59	$259.60	$259.60
Purchase #4	$134.90	13.144%	$152.6313	$152.63	$152.65	$152.60
Purchase #5	$231.90	10.140%	$255.4147	$255.41	$255.40	$255.40
Purchase #6	$227.32	9.205%	$248.2448	$248.24	$248.25	$248.20
Purchase #7	$96.90	9.781%	$106.3778	$106.38	$106.40	$106.40
7 purchase totals =	$1,069.58		$1,162.3586	$1,162.34	$1,162.40	$1,162.30