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	$61.93	5.456%	$65.3089	$65.31	$65.30	$65.30
Purchase #2	$53.44	5.603%	$56.4342	$56.43	$56.45	$56.40
Purchase #3	$155.98	4.604%	$163.1613	$163.16	$163.15	$163.20
Purchase #4	$82.79	8.594%	$89.905	$89.91	$89.90	$89.90
Purchase #5	$61.27	13.218%	$69.3687	$69.37	$69.35	$69.40
Purchase #6	$48.90	9.444%	$53.5181	$53.52	$53.50	$53.50
Purchase #7	$223.78	9.746%	$245.5896	$245.59	$245.60	$245.60
7 purchase totals =	$688.09		$743.2858	$743.29	$743.25	$743.30