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	$163.68	13.339%	$185.5133	$185.51	$185.50	$185.50
Purchase #2	$150.28	9.252%	$164.1839	$164.18	$164.20	$164.20
Purchase #3	$21.75	6.401%	$23.1422	$23.14	$23.15	$23.10
Purchase #4	$143.61	9.287%	$156.9471	$156.95	$156.95	$156.90
Purchase #5	$117.93	3.405%	$121.9455	$121.95	$121.95	$121.90
Purchase #6	$118.51	4.188%	$123.4732	$123.47	$123.45	$123.50
Purchase #7	$89.47	10.602%	$98.9556	$98.96	$98.95	$99.00
7 purchase totals =	$805.23		$874.1608	$874.16	$874.15	$874.10