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	$227.76	13.687%	$258.9335	$258.93	$258.95	$258.90
Purchase #2	$99.71	13.698%	$113.3683	$113.37	$113.35	$113.40
Purchase #3	$34.70	7.488%	$37.2983	$37.30	$37.30	$37.30
Purchase #4	$165.47	4.772%	$173.3662	$173.37	$173.35	$173.40
Purchase #5	$150.28	4.108%	$156.4535	$156.45	$156.45	$156.50
Purchase #6	$19.54	3.332%	$20.1911	$20.19	$20.20	$20.20
Purchase #7	$230.85	11.437%	$257.2523	$257.25	$257.25	$257.30
7 purchase totals =	$928.31		$1,016.8632	$1,016.86	$1,016.85	$1,017.00