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	$190.32	13.137%	$215.3223	$215.32	$215.30	$215.30
Purchase #2	$125.53	5.523%	$132.463	$132.46	$132.45	$132.50
Purchase #3	$170.59	8.574%	$185.2164	$185.22	$185.20	$185.20
Purchase #4	$160.75	13.237%	$182.0285	$182.03	$182.05	$182.00
Purchase #5	$64.25	4.509%	$67.147	$67.15	$67.15	$67.10
Purchase #6	$166.50	12.113%	$186.6681	$186.67	$186.65	$186.70
Purchase #7	$173.96	8.385%	$188.5465	$188.55	$188.55	$188.50
7 purchase totals =	$1,051.90		$1,157.3918	$1,157.40	$1,157.35	$1,157.30