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	$172.94	13.678%	$196.5947	$196.59	$196.60	$196.60
Purchase #2	$133.51	13.137%	$151.0492	$151.05	$151.05	$151.00
Purchase #3	$108.70	3.200%	$112.1784	$112.18	$112.20	$112.20
Purchase #4	$85.43	4.278%	$89.0847	$89.08	$89.10	$89.10
Purchase #5	$50.70	12.511%	$57.0431	$57.04	$57.05	$57.00
Purchase #6	$155.52	10.853%	$172.3986	$172.40	$172.40	$172.40
Purchase #7	$199.65	12.210%	$224.0273	$224.03	$224.05	$224.00
7 purchase totals =	$906.45		$1,002.3760	$1,002.37	$1,002.45	$1,002.30