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	$233.74	11.771%	$261.2535	$261.25	$261.25	$261.30
Purchase #2	$83.42	11.309%	$92.854	$92.85	$92.85	$92.90
Purchase #3	$78.60	9.506%	$86.0717	$86.07	$86.05	$86.10
Purchase #4	$156.78	4.376%	$163.6407	$163.64	$163.65	$163.60
Purchase #5	$137.93	12.479%	$155.1423	$155.14	$155.15	$155.10
Purchase #6	$59.69	12.438%	$67.1142	$67.11	$67.10	$67.10
Purchase #7	$245.79	13.734%	$279.5468	$279.55	$279.55	$279.50
7 purchase totals =	$995.95		$1,105.6232	$1,105.61	$1,105.60	$1,105.60