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	$84.76	6.739%	$90.472	$90.47	$90.45	$90.50
Purchase #2	$194.52	9.220%	$212.4547	$212.45	$212.45	$212.50
Purchase #3	$144.87	9.501%	$158.6341	$158.63	$158.65	$158.60
Purchase #4	$128.34	9.325%	$140.3077	$140.31	$140.30	$140.30
Purchase #5	$92.88	9.246%	$101.4677	$101.47	$101.45	$101.50
Purchase #6	$19.42	6.525%	$20.6872	$20.69	$20.70	$20.70
Purchase #7	$209.93	8.568%	$227.9168	$227.92	$227.90	$227.90
7 purchase totals =	$874.72		$951.9402	$951.94	$951.90	$952.00