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	$32.55	6.349%	$34.6166	$34.62	$34.60	$34.60
Purchase #2	$114.93	7.537%	$123.5923	$123.59	$123.60	$123.60
Purchase #3	$152.58	13.487%	$173.1585	$173.16	$173.15	$173.20
Purchase #4	$29.76	10.218%	$32.8009	$32.80	$32.80	$32.80
Purchase #5	$22.86	13.666%	$25.984	$25.98	$26.00	$26.00
Purchase #6	$137.36	10.355%	$151.5836	$151.58	$151.60	$151.60
Purchase #7	$127.34	11.116%	$141.4951	$141.50	$141.50	$141.50
7 purchase totals =	$617.38		$683.2310	$683.23	$683.25	$683.30