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	$146.48	3.531%	$151.6522	$151.65	$151.65	$151.70
Purchase #2	$126.62	6.521%	$134.8769	$134.88	$134.90	$134.90
Purchase #3	$196.76	10.104%	$216.6406	$216.64	$216.65	$216.60
Purchase #4	$248.67	12.509%	$279.7761	$279.78	$279.80	$279.80
Purchase #5	$198.75	4.375%	$207.4453	$207.45	$207.45	$207.40
Purchase #6	$30.52	5.234%	$32.1174	$32.12	$32.10	$32.10
Purchase #7	$80.50	11.591%	$89.8308	$89.83	$89.85	$89.80
7 purchase totals =	$1,028.30		$1,112.3393	$1,112.35	$1,112.40	$1,112.30