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	$10.68	7.385%	$11.4687	$11.47	$11.45	$11.50
Purchase #2	$28.92	13.848%	$32.9248	$32.92	$32.90	$32.90
Purchase #3	$63.82	10.425%	$70.4732	$70.47	$70.45	$70.50
Purchase #4	$34.52	7.835%	$37.2246	$37.22	$37.20	$37.20
Purchase #5	$191.72	3.774%	$198.9555	$198.96	$198.95	$199.00
Purchase #6	$165.77	11.770%	$185.2811	$185.28	$185.30	$185.30
Purchase #7	$222.62	7.297%	$238.8646	$238.86	$238.85	$238.90
7 purchase totals =	$718.05		$775.1925	$775.18	$775.10	$775.30