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	$202.59	13.503%	$229.9457	$229.95	$229.95	$229.90
Purchase #2	$91.27	13.531%	$103.6197	$103.62	$103.60	$103.60
Purchase #3	$99.87	5.778%	$105.6405	$105.64	$105.65	$105.60
Purchase #4	$153.44	8.287%	$166.1556	$166.16	$166.15	$166.20
Purchase #5	$141.32	12.407%	$158.8536	$158.85	$158.85	$158.90
Purchase #6	$217.59	11.192%	$241.9427	$241.94	$241.95	$241.90
Purchase #7	$29.29	12.340%	$32.9044	$32.90	$32.90	$32.90
7 purchase totals =	$935.37		$1,039.0622	$1,039.06	$1,039.05	$1,039.00