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	$186.83	7.289%	$200.448	$200.45	$200.45	$200.40
Purchase #2	$133.35	8.358%	$144.4954	$144.50	$144.50	$144.50
Purchase #3	$216.37	12.161%	$242.6828	$242.68	$242.70	$242.70
Purchase #4	$214.45	4.398%	$223.8815	$223.88	$223.90	$223.90
Purchase #5	$57.69	4.776%	$60.4453	$60.45	$60.45	$60.40
Purchase #6	$111.33	3.510%	$115.2377	$115.24	$115.25	$115.20
Purchase #7	$7.51	4.342%	$7.8361	$7.84	$7.85	$7.80
7 purchase totals =	$927.53		$995.0268	$995.04	$995.10	$994.90