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	$98.57	7.508%	$105.9706	$105.97	$105.95	$106.00
Purchase #2	$118.76	7.708%	$127.914	$127.91	$127.90	$127.90
Purchase #3	$39.50	5.713%	$41.7566	$41.76	$41.75	$41.80
Purchase #4	$55.72	11.729%	$62.2554	$62.26	$62.25	$62.30
Purchase #5	$34.63	8.467%	$37.5621	$37.56	$37.55	$37.60
Purchase #6	$196.98	5.657%	$208.1232	$208.12	$208.10	$208.10
Purchase #7	$7.52	12.299%	$8.4449	$8.44	$8.45	$8.40
7 purchase totals =	$551.68		$592.0268	$592.02	$591.95	$592.10