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	$94.55	4.847%	$99.1328	$99.13	$99.15	$99.10
Purchase #2	$126.49	8.374%	$137.0823	$137.08	$137.10	$137.10
Purchase #3	$92.73	6.617%	$98.8659	$98.87	$98.85	$98.90
Purchase #4	$184.92	4.140%	$192.5757	$192.58	$192.60	$192.60
Purchase #5	$115.59	13.772%	$131.5091	$131.51	$131.50	$131.50
Purchase #6	$94.52	4.241%	$98.5286	$98.53	$98.55	$98.50
Purchase #7	$111.91	7.843%	$120.6871	$120.69	$120.70	$120.70
7 purchase totals =	$820.71		$878.3815	$878.39	$878.45	$878.40