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	$206.47	5.800%	$218.4453	$218.45	$218.45	$218.40
Purchase #2	$62.91	11.425%	$70.0975	$70.10	$70.10	$70.10
Purchase #3	$244.85	4.320%	$255.4275	$255.43	$255.45	$255.40
Purchase #4	$168.85	12.316%	$189.6456	$189.65	$189.65	$189.60
Purchase #5	$37.55	12.822%	$42.3647	$42.36	$42.35	$42.40
Purchase #6	$110.99	4.866%	$116.3908	$116.39	$116.40	$116.40
Purchase #7	$145.94	5.106%	$153.3917	$153.39	$153.40	$153.40
7 purchase totals =	$977.56		$1,045.7631	$1,045.77	$1,045.80	$1,045.70