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	$63.43	12.701%	$71.4862	$71.49	$71.50	$71.50
Purchase #2	$134.38	12.624%	$151.3441	$151.34	$151.35	$151.30
Purchase #3	$132.55	9.742%	$145.463	$145.46	$145.45	$145.50
Purchase #4	$177.27	12.637%	$199.6716	$199.67	$199.65	$199.70
Purchase #5	$154.80	8.469%	$167.91	$167.91	$167.90	$167.90
Purchase #6	$10.67	8.815%	$11.6106	$11.61	$11.60	$11.60
Purchase #7	$31.42	12.149%	$35.2372	$35.24	$35.25	$35.20
7 purchase totals =	$704.52		$782.7227	$782.72	$782.70	$782.70