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	$117.51	12.462%	$132.1541	$132.15	$132.15	$132.20
Purchase #2	$238.91	7.758%	$257.4446	$257.44	$257.45	$257.40
Purchase #3	$107.29	4.854%	$112.4979	$112.50	$112.50	$112.50
Purchase #4	$77.28	4.770%	$80.9663	$80.97	$80.95	$81.00
Purchase #5	$71.91	9.321%	$78.6127	$78.61	$78.60	$78.60
Purchase #6	$179.72	3.240%	$185.5429	$185.54	$185.55	$185.50
Purchase #7	$60.82	7.731%	$65.522	$65.52	$65.50	$65.50
7 purchase totals =	$853.44		$912.7405	$912.73	$912.70	$912.70