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	$183.36	4.572%	$191.7432	$191.74	$191.75	$191.70
Purchase #2	$234.58	10.604%	$259.4549	$259.45	$259.45	$259.50
Purchase #3	$181.29	4.292%	$189.071	$189.07	$189.05	$189.10
Purchase #4	$44.27	5.729%	$46.8062	$46.81	$46.80	$46.80
Purchase #5	$94.54	10.623%	$104.583	$104.58	$104.60	$104.60
Purchase #6	$137.62	11.716%	$153.7436	$153.74	$153.75	$153.70
Purchase #7	$148.92	4.142%	$155.0883	$155.09	$155.10	$155.10
7 purchase totals =	$1,024.58		$1,100.4902	$1,100.48	$1,100.50	$1,100.50