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	$117.38	11.408%	$130.7707	$130.77	$130.75	$130.80
Purchase #2	$54.97	12.344%	$61.7555	$61.76	$61.75	$61.80
Purchase #3	$226.30	5.196%	$238.0585	$238.06	$238.05	$238.10
Purchase #4	$182.96	4.163%	$190.5766	$190.58	$190.60	$190.60
Purchase #5	$94.27	9.336%	$103.071	$103.07	$103.05	$103.10
Purchase #6	$189.84	4.766%	$198.8878	$198.89	$198.90	$198.90
Purchase #7	$249.51	9.223%	$272.5223	$272.52	$272.50	$272.50
7 purchase totals =	$1,115.23		$1,195.6424	$1,195.65	$1,195.60	$1,195.80