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	$137.53	10.446%	$151.8964	$151.90	$151.90	$151.90
Purchase #2	$230.77	10.338%	$254.627	$254.63	$254.65	$254.60
Purchase #3	$166.31	3.753%	$172.5516	$172.55	$172.55	$172.60
Purchase #4	$33.29	5.114%	$34.9925	$34.99	$35.00	$35.00
Purchase #5	$213.67	10.280%	$235.6353	$235.64	$235.65	$235.60
Purchase #6	$95.49	8.297%	$103.4128	$103.41	$103.40	$103.40
Purchase #7	$90.56	4.466%	$94.6044	$94.60	$94.60	$94.60
7 purchase totals =	$967.62		$1,047.7200	$1,047.72	$1,047.75	$1,047.70