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	$142.44	9.788%	$156.382	$156.38	$156.40	$156.40
Purchase #2	$247.99	3.123%	$255.7347	$255.73	$255.75	$255.70
Purchase #3	$214.39	12.471%	$241.1266	$241.13	$241.15	$241.10
Purchase #4	$58.98	13.321%	$66.8367	$66.84	$66.85	$66.80
Purchase #5	$71.75	9.610%	$78.6452	$78.65	$78.65	$78.60
Purchase #6	$17.60	3.354%	$18.1903	$18.19	$18.20	$18.20
Purchase #7	$211.80	10.508%	$234.0559	$234.06	$234.05	$234.10
7 purchase totals =	$964.95		$1,050.9714	$1,050.98	$1,051.05	$1,050.90