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	$62.59	8.679%	$68.0222	$68.02	$68.00	$68.00
Purchase #2	$80.35	6.360%	$85.4603	$85.46	$85.45	$85.50
Purchase #3	$104.27	10.514%	$115.2329	$115.23	$115.25	$115.20
Purchase #4	$250.83	5.157%	$263.7653	$263.77	$263.75	$263.80
Purchase #5	$132.86	6.808%	$141.9051	$141.91	$141.90	$141.90
Purchase #6	$122.82	13.358%	$139.2263	$139.23	$139.25	$139.20
Purchase #7	$47.90	11.822%	$53.5627	$53.56	$53.55	$53.60
7 purchase totals =	$801.62		$867.1748	$867.18	$867.15	$867.20