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	$52.95	9.404%	$57.9294	$57.93	$57.95	$57.90
Purchase #2	$75.82	9.337%	$82.8993	$82.90	$82.90	$82.90
Purchase #3	$151.41	11.738%	$169.1825	$169.18	$169.20	$169.20
Purchase #4	$103.39	9.418%	$113.1273	$113.13	$113.15	$113.10
Purchase #5	$9.56	4.617%	$10.0014	$10.00	$10.00	$10.00
Purchase #6	$78.53	11.573%	$87.6183	$87.62	$87.60	$87.60
Purchase #7	$228.53	5.607%	$241.3437	$241.34	$241.35	$241.30
7 purchase totals =	$700.19		$762.1019	$762.10	$762.15	$762.00