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	$53.58	9.342%	$58.5854	$58.59	$58.60	$58.60
Purchase #2	$35.61	4.312%	$37.1455	$37.15	$37.15	$37.10
Purchase #3	$47.71	9.112%	$52.0573	$52.06	$52.05	$52.10
Purchase #4	$46.54	10.160%	$51.2685	$51.27	$51.25	$51.30
Purchase #5	$96.89	4.637%	$101.3828	$101.38	$101.40	$101.40
Purchase #6	$74.60	4.245%	$77.7668	$77.77	$77.75	$77.80
Purchase #7	$223.60	5.417%	$235.7124	$235.71	$235.70	$235.70
7 purchase totals =	$578.53		$613.9187	$613.93	$613.90	$614.00