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	$14.46	7.712%	$15.5752	$15.58	$15.60	$15.60
Purchase #2	$24.67	3.449%	$25.5209	$25.52	$25.50	$25.50
Purchase #3	$80.73	10.363%	$89.096	$89.10	$89.10	$89.10
Purchase #4	$21.55	3.255%	$22.2515	$22.25	$22.25	$22.30
Purchase #5	$118.80	7.822%	$128.0925	$128.09	$128.10	$128.10
Purchase #6	$10.68	10.720%	$11.8249	$11.82	$11.80	$11.80
Purchase #7	$138.89	3.227%	$143.372	$143.37	$143.35	$143.40
7 purchase totals =	$409.78		$435.7330	$435.73	$435.70	$435.80