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	$133.84	8.821%	$145.646	$145.65	$145.65	$145.60
Purchase #2	$244.33	5.771%	$258.4303	$258.43	$258.45	$258.40
Purchase #3	$38.89	8.332%	$42.1303	$42.13	$42.15	$42.10
Purchase #4	$214.62	9.140%	$234.2363	$234.24	$234.25	$234.20
Purchase #5	$187.70	4.522%	$196.1878	$196.19	$196.20	$196.20
Purchase #6	$98.28	7.243%	$105.3984	$105.40	$105.40	$105.40
Purchase #7	$62.28	5.361%	$65.6188	$65.62	$65.60	$65.60
7 purchase totals =	$979.94		$1,047.6479	$1,047.66	$1,047.70	$1,047.50