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	$79.66	3.142%	$82.1629	$82.16	$82.15	$82.20
Purchase #2	$143.98	12.244%	$161.6089	$161.61	$161.60	$161.60
Purchase #3	$115.52	5.594%	$121.9822	$121.98	$122.00	$122.00
Purchase #4	$125.57	4.579%	$131.3199	$131.32	$131.30	$131.30
Purchase #5	$83.43	3.459%	$86.3158	$86.32	$86.30	$86.30
Purchase #6	$94.92	11.248%	$105.5966	$105.60	$105.60	$105.60
Purchase #7	$15.71	5.654%	$16.5982	$16.60	$16.60	$16.60
7 purchase totals =	$658.79		$705.5845	$705.59	$705.55	$705.60