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	$215.50	3.313%	$222.6395	$222.64	$222.65	$222.60
Purchase #2	$241.49	6.795%	$257.8992	$257.90	$257.90	$257.90
Purchase #3	$135.82	6.684%	$144.8982	$144.90	$144.90	$144.90
Purchase #4	$97.27	13.385%	$110.2896	$110.29	$110.30	$110.30
Purchase #5	$167.50	11.469%	$186.7106	$186.71	$186.70	$186.70
Purchase #6	$49.70	8.539%	$53.9439	$53.94	$53.95	$53.90
Purchase #7	$166.27	4.761%	$174.1861	$174.19	$174.20	$174.20
7 purchase totals =	$1,073.55		$1,150.5671	$1,150.57	$1,150.60	$1,150.50