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	$196.29	10.246%	$216.4019	$216.40	$216.40	$216.40
Purchase #2	$105.69	5.799%	$111.819	$111.82	$111.80	$111.80
Purchase #3	$198.76	10.482%	$219.594	$219.59	$219.60	$219.60
Purchase #4	$207.60	8.550%	$225.3498	$225.35	$225.35	$225.30
Purchase #5	$116.90	10.109%	$128.7174	$128.72	$128.70	$128.70
Purchase #6	$149.40	12.674%	$168.335	$168.34	$168.35	$168.30
Purchase #7	$16.64	12.753%	$18.7621	$18.76	$18.75	$18.80
7 purchase totals =	$991.28		$1,088.9792	$1,088.98	$1,088.95	$1,088.90