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	$110.81	3.771%	$114.9886	$114.99	$115.00	$115.00
Purchase #2	$35.42	11.441%	$39.4724	$39.47	$39.45	$39.50
Purchase #3	$55.64	7.433%	$59.7757	$59.78	$59.80	$59.80
Purchase #4	$15.27	13.116%	$17.2728	$17.27	$17.25	$17.30
Purchase #5	$54.95	8.655%	$59.7059	$59.71	$59.70	$59.70
Purchase #6	$211.68	11.304%	$235.6083	$235.61	$235.60	$235.60
Purchase #7	$95.27	9.807%	$104.6131	$104.61	$104.60	$104.60
7 purchase totals =	$579.04		$631.4368	$631.44	$631.40	$631.50