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	$19.88	3.806%	$20.6366	$20.64	$20.65	$20.60
Purchase #2	$65.29	9.377%	$71.4122	$71.41	$71.40	$71.40
Purchase #3	$68.37	6.596%	$72.8797	$72.88	$72.90	$72.90
Purchase #4	$11.54	4.817%	$12.0959	$12.10	$12.10	$12.10
Purchase #5	$47.62	3.739%	$49.4005	$49.40	$49.40	$49.40
Purchase #6	$115.51	7.439%	$124.1028	$124.10	$124.10	$124.10
Purchase #7	$175.93	3.711%	$182.4588	$182.46	$182.45	$182.50
7 purchase totals =	$504.14		$532.9865	$532.99	$533.00	$533.00