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	$134.79	10.830%	$149.3878	$149.39	$149.40	$149.40
Purchase #2	$86.59	6.504%	$92.2218	$92.22	$92.20	$92.20
Purchase #3	$39.34	12.507%	$44.2603	$44.26	$44.25	$44.30
Purchase #4	$154.92	8.723%	$168.4337	$168.43	$168.45	$168.40
Purchase #5	$104.42	6.601%	$111.3128	$111.31	$111.30	$111.30
Purchase #6	$120.89	5.784%	$127.8823	$127.88	$127.90	$127.90
Purchase #7	$22.93	5.654%	$24.2265	$24.23	$24.25	$24.20
7 purchase totals =	$663.88		$717.7252	$717.72	$717.75	$717.70