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	$54.90	7.743%	$59.1509	$59.15	$59.15	$59.20
Purchase #2	$234.72	5.806%	$248.3478	$248.35	$248.35	$248.30
Purchase #3	$181.85	4.488%	$190.0114	$190.01	$190.00	$190.00
Purchase #4	$103.69	10.228%	$114.2954	$114.30	$114.30	$114.30
Purchase #5	$21.42	9.453%	$23.4448	$23.44	$23.45	$23.40
Purchase #6	$207.32	4.409%	$216.4607	$216.46	$216.45	$216.50
Purchase #7	$191.74	10.699%	$212.2543	$212.25	$212.25	$212.30
7 purchase totals =	$995.64		$1,063.9653	$1,063.96	$1,063.95	$1,064.00