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	$207.76	8.687%	$225.8081	$225.81	$225.80	$225.80
Purchase #2	$15.89	3.663%	$16.4721	$16.47	$16.45	$16.50
Purchase #3	$233.84	8.678%	$254.1326	$254.13	$254.15	$254.10
Purchase #4	$54.78	3.302%	$56.5888	$56.59	$56.60	$56.60
Purchase #5	$185.74	10.828%	$205.8519	$205.85	$205.85	$205.90
Purchase #6	$107.41	4.112%	$111.8267	$111.83	$111.85	$111.80
Purchase #7	$204.80	3.215%	$211.3843	$211.38	$211.40	$211.40
7 purchase totals =	$1,010.22		$1,082.0645	$1,082.06	$1,082.10	$1,082.10