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	$158.65	5.519%	$167.4059	$167.41	$167.40	$167.40
Purchase #2	$31.68	13.721%	$36.0268	$36.03	$36.05	$36.00
Purchase #3	$19.97	5.373%	$21.043	$21.04	$21.05	$21.00
Purchase #4	$24.52	12.317%	$27.5401	$27.54	$27.55	$27.50
Purchase #5	$99.74	12.103%	$111.8115	$111.81	$111.80	$111.80
Purchase #6	$63.51	6.841%	$67.8547	$67.85	$67.85	$67.90
Purchase #7	$45.80	9.493%	$50.1478	$50.15	$50.15	$50.10
7 purchase totals =	$443.87		$481.8298	$481.83	$481.85	$481.70