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	$156.82	11.499%	$174.8527	$174.85	$174.85	$174.90
Purchase #2	$37.52	10.637%	$41.511	$41.51	$41.50	$41.50
Purchase #3	$11.89	4.474%	$12.422	$12.42	$12.40	$12.40
Purchase #4	$40.57	3.626%	$42.0411	$42.04	$42.05	$42.00
Purchase #5	$174.39	11.709%	$194.8093	$194.81	$194.80	$194.80
Purchase #6	$133.37	13.562%	$151.4576	$151.46	$151.45	$151.50
Purchase #7	$207.71	12.194%	$233.0382	$233.04	$233.05	$233.00
7 purchase totals =	$762.27		$850.1319	$850.13	$850.10	$850.10