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	$97.91	5.258%	$103.0581	$103.06	$103.05	$103.10
Purchase #2	$192.95	7.581%	$207.5775	$207.58	$207.60	$207.60
Purchase #3	$54.45	3.148%	$56.1641	$56.16	$56.15	$56.20
Purchase #4	$215.40	10.727%	$238.506	$238.51	$238.50	$238.50
Purchase #5	$22.62	11.194%	$25.1521	$25.15	$25.15	$25.20
Purchase #6	$179.33	11.719%	$200.3457	$200.35	$200.35	$200.30
Purchase #7	$228.32	11.707%	$255.0494	$255.05	$255.05	$255.00
7 purchase totals =	$990.98		$1,085.8529	$1,085.86	$1,085.85	$1,085.90