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	$187.85	5.685%	$198.5293	$198.53	$198.55	$198.50
Purchase #2	$107.83	3.647%	$111.7626	$111.76	$111.75	$111.80
Purchase #3	$223.48	6.738%	$238.5381	$238.54	$238.55	$238.50
Purchase #4	$93.76	10.762%	$103.8505	$103.85	$103.85	$103.90
Purchase #5	$35.77	4.213%	$37.277	$37.28	$37.30	$37.30
Purchase #6	$183.52	7.563%	$197.3996	$197.40	$197.40	$197.40
Purchase #7	$126.66	3.184%	$130.6929	$130.69	$130.70	$130.70
7 purchase totals =	$958.87		$1,018.0500	$1,018.05	$1,018.10	$1,018.10