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	$226.70	10.383%	$250.2383	$250.24	$250.25	$250.20
Purchase #2	$212.60	9.685%	$233.1903	$233.19	$233.20	$233.20
Purchase #3	$108.65	4.705%	$113.762	$113.76	$113.75	$113.80
Purchase #4	$127.75	12.297%	$143.4594	$143.46	$143.45	$143.50
Purchase #5	$211.30	5.116%	$222.1101	$222.11	$222.10	$222.10
Purchase #6	$132.89	7.196%	$142.4528	$142.45	$142.45	$142.50
Purchase #7	$247.41	4.458%	$258.4395	$258.44	$258.45	$258.40
7 purchase totals =	$1,267.30		$1,363.6524	$1,363.65	$1,363.65	$1,363.70