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	$151.61	10.329%	$167.2698	$167.27	$167.25	$167.30
Purchase #2	$145.43	12.498%	$163.6058	$163.61	$163.60	$163.60
Purchase #3	$132.71	11.705%	$148.2437	$148.24	$148.25	$148.20
Purchase #4	$211.55	5.495%	$223.1747	$223.17	$223.15	$223.20
Purchase #5	$185.75	9.613%	$203.6061	$203.61	$203.60	$203.60
Purchase #6	$76.64	8.171%	$82.9023	$82.90	$82.90	$82.90
Purchase #7	$77.98	4.570%	$81.5437	$81.54	$81.55	$81.50
7 purchase totals =	$981.67		$1,070.3461	$1,070.34	$1,070.30	$1,070.30