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	$60.66	10.285%	$66.8989	$66.90	$66.90	$66.90
Purchase #2	$50.43	5.762%	$53.3358	$53.34	$53.35	$53.30
Purchase #3	$38.37	3.119%	$39.5668	$39.57	$39.55	$39.60
Purchase #4	$30.62	13.648%	$34.799	$34.80	$34.80	$34.80
Purchase #5	$160.47	4.332%	$167.4216	$167.42	$167.40	$167.40
Purchase #6	$59.36	3.348%	$61.3474	$61.35	$61.35	$61.30
Purchase #7	$66.25	8.233%	$71.7044	$71.70	$71.70	$71.70
7 purchase totals =	$466.16		$495.0739	$495.08	$495.05	$495.00