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	$118.53	11.603%	$132.283	$132.28	$132.30	$132.30
Purchase #2	$110.54	7.326%	$118.6382	$118.64	$118.65	$118.60
Purchase #3	$40.28	7.640%	$43.3574	$43.36	$43.35	$43.40
Purchase #4	$29.83	9.363%	$32.623	$32.62	$32.60	$32.60
Purchase #5	$38.32	4.730%	$40.1325	$40.13	$40.15	$40.10
Purchase #6	$173.86	13.637%	$197.5693	$197.57	$197.55	$197.60
Purchase #7	$112.91	12.786%	$127.3467	$127.35	$127.35	$127.30
7 purchase totals =	$624.27		$691.9501	$691.95	$691.95	$691.90