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	$159.91	9.520%	$175.1334	$175.13	$175.15	$175.10
Purchase #2	$107.46	3.383%	$111.0954	$111.10	$111.10	$111.10
Purchase #3	$61.61	6.403%	$65.5549	$65.55	$65.55	$65.60
Purchase #4	$100.30	12.252%	$112.5888	$112.59	$112.60	$112.60
Purchase #5	$250.60	5.792%	$265.1148	$265.11	$265.10	$265.10
Purchase #6	$153.52	5.733%	$162.3213	$162.32	$162.30	$162.30
Purchase #7	$43.92	9.209%	$47.9646	$47.96	$47.95	$48.00
7 purchase totals =	$877.32		$939.7732	$939.76	$939.75	$939.80