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	$188.69	8.831%	$205.3532	$205.35	$205.35	$205.40
Purchase #2	$49.25	5.725%	$52.0696	$52.07	$52.05	$52.10
Purchase #3	$54.66	5.368%	$57.5941	$57.59	$57.60	$57.60
Purchase #4	$125.88	5.472%	$132.7682	$132.77	$132.75	$132.80
Purchase #5	$35.29	5.255%	$37.1445	$37.14	$37.15	$37.10
Purchase #6	$246.39	9.768%	$270.4574	$270.46	$270.45	$270.50
Purchase #7	$131.37	10.240%	$144.8223	$144.82	$144.80	$144.80
7 purchase totals =	$831.53		$900.2093	$900.20	$900.15	$900.30