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	$70.25	11.768%	$78.517	$78.52	$78.50	$78.50
Purchase #2	$118.50	10.510%	$130.9544	$130.95	$130.95	$131.00
Purchase #3	$151.83	5.337%	$159.9332	$159.93	$159.95	$159.90
Purchase #4	$14.28	10.264%	$15.7457	$15.75	$15.75	$15.70
Purchase #5	$104.93	9.102%	$114.4807	$114.48	$114.50	$114.50
Purchase #6	$10.65	6.525%	$11.3449	$11.34	$11.35	$11.30
Purchase #7	$213.35	11.662%	$238.2309	$238.23	$238.25	$238.20
7 purchase totals =	$683.79		$749.2068	$749.20	$749.25	$749.10