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	$173.35	13.182%	$196.201	$196.20	$196.20	$196.20
Purchase #2	$129.47	10.169%	$142.6358	$142.64	$142.65	$142.60
Purchase #3	$137.67	10.510%	$152.1391	$152.14	$152.15	$152.10
Purchase #4	$58.85	12.220%	$66.0415	$66.04	$66.05	$66.00
Purchase #5	$26.57	6.857%	$28.3919	$28.39	$28.40	$28.40
Purchase #6	$104.47	5.785%	$110.5136	$110.51	$110.50	$110.50
Purchase #7	$128.59	4.574%	$134.4717	$134.47	$134.45	$134.50
7 purchase totals =	$758.97		$830.3946	$830.39	$830.40	$830.30