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	$153.56	12.410%	$172.6168	$172.62	$172.60	$172.60
Purchase #2	$175.64	6.156%	$186.4524	$186.45	$186.45	$186.50
Purchase #3	$45.78	5.805%	$48.4375	$48.44	$48.45	$48.40
Purchase #4	$205.40	3.663%	$212.9238	$212.92	$212.90	$212.90
Purchase #5	$155.27	6.546%	$165.434	$165.43	$165.45	$165.40
Purchase #6	$139.55	6.258%	$148.283	$148.28	$148.30	$148.30
Purchase #7	$210.27	7.441%	$225.9162	$225.92	$225.90	$225.90
7 purchase totals =	$1,085.47		$1,160.0637	$1,160.06	$1,160.05	$1,160.00