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	$57.77	7.803%	$62.2778	$62.28	$62.30	$62.30
Purchase #2	$181.37	8.139%	$196.1317	$196.13	$196.15	$196.10
Purchase #3	$82.76	12.257%	$92.9039	$92.90	$92.90	$92.90
Purchase #4	$105.80	10.444%	$116.8498	$116.85	$116.85	$116.80
Purchase #5	$8.38	11.596%	$9.3517	$9.35	$9.35	$9.40
Purchase #6	$9.87	4.450%	$10.3092	$10.31	$10.30	$10.30
Purchase #7	$10.86	7.682%	$11.6943	$11.69	$11.70	$11.70
7 purchase totals =	$456.81		$499.5184	$499.51	$499.55	$499.50