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	$219.98	3.583%	$227.8619	$227.86	$227.85	$227.90
Purchase #2	$244.81	12.702%	$275.9058	$275.91	$275.90	$275.90
Purchase #3	$137.97	8.308%	$149.4325	$149.43	$149.45	$149.40
Purchase #4	$47.63	5.118%	$50.0677	$50.07	$50.05	$50.10
Purchase #5	$216.69	10.104%	$238.5844	$238.58	$238.60	$238.60
Purchase #6	$81.52	9.506%	$89.2693	$89.27	$89.25	$89.30
Purchase #7	$156.25	11.274%	$173.8656	$173.87	$173.85	$173.90
7 purchase totals =	$1,104.85		$1,204.9872	$1,204.99	$1,204.95	$1,205.10