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	$198.91	6.465%	$211.7695	$211.77	$211.75	$211.80
Purchase #2	$49.69	9.296%	$54.3092	$54.31	$54.30	$54.30
Purchase #3	$153.34	10.549%	$169.5158	$169.52	$169.50	$169.50
Purchase #4	$173.64	5.746%	$183.6174	$183.62	$183.60	$183.60
Purchase #5	$89.97	11.227%	$100.0709	$100.07	$100.05	$100.10
Purchase #6	$70.25	3.492%	$72.7031	$72.70	$72.70	$72.70
Purchase #7	$250.71	3.871%	$260.415	$260.42	$260.40	$260.40
7 purchase totals =	$986.51		$1,052.4009	$1,052.41	$1,052.30	$1,052.40