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	$41.27	11.583%	$46.0503	$46.05	$46.05	$46.10
Purchase #2	$29.61	6.374%	$31.4973	$31.50	$31.50	$31.50
Purchase #3	$46.61	6.439%	$49.6112	$49.61	$49.60	$49.60
Purchase #4	$65.75	7.866%	$70.9219	$70.92	$70.90	$70.90
Purchase #5	$107.75	3.715%	$111.7529	$111.75	$111.75	$111.80
Purchase #6	$19.29	5.704%	$20.3903	$20.39	$20.40	$20.40
Purchase #7	$73.57	9.416%	$80.4974	$80.50	$80.50	$80.50
7 purchase totals =	$383.85		$410.7213	$410.72	$410.70	$410.80