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	$226.26	11.808%	$252.9768	$252.98	$253.00	$253.00
Purchase #2	$148.87	5.379%	$156.8777	$156.88	$156.90	$156.90
Purchase #3	$159.42	9.806%	$175.0527	$175.05	$175.05	$175.10
Purchase #4	$50.82	6.508%	$54.1274	$54.13	$54.15	$54.10
Purchase #5	$85.28	6.196%	$90.5639	$90.56	$90.55	$90.60
Purchase #6	$77.57	10.669%	$85.8459	$85.85	$85.85	$85.80
Purchase #7	$224.69	11.128%	$249.6935	$249.69	$249.70	$249.70
7 purchase totals =	$972.91		$1,065.1379	$1,065.14	$1,065.20	$1,065.20