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	$132.28	7.436%	$142.1163	$142.12	$142.10	$142.10
Purchase #2	$98.45	13.140%	$111.3863	$111.39	$111.40	$111.40
Purchase #3	$104.43	3.491%	$108.0757	$108.08	$108.10	$108.10
Purchase #4	$75.39	3.283%	$77.8651	$77.87	$77.85	$77.90
Purchase #5	$244.51	6.649%	$260.7675	$260.77	$260.75	$260.80
Purchase #6	$203.29	10.419%	$224.4708	$224.47	$224.45	$224.50
Purchase #7	$57.88	5.494%	$61.0599	$61.06	$61.05	$61.10
7 purchase totals =	$916.23		$985.7416	$985.76	$985.70	$985.90