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	$141.26	5.812%	$149.47	$149.47	$149.45	$149.50
Purchase #2	$31.98	11.276%	$35.5861	$35.59	$35.60	$35.60
Purchase #3	$188.51	6.563%	$200.8819	$200.88	$200.90	$200.90
Purchase #4	$237.64	12.236%	$266.7176	$266.72	$266.70	$266.70
Purchase #5	$158.53	8.150%	$171.4502	$171.45	$171.45	$171.50
Purchase #6	$35.35	13.521%	$40.1297	$40.13	$40.15	$40.10
Purchase #7	$247.66	9.777%	$271.8737	$271.87	$271.85	$271.90
7 purchase totals =	$1,040.93		$1,136.1092	$1,136.11	$1,136.10	$1,136.20