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	$53.94	11.190%	$59.9759	$59.98	$60.00	$60.00
Purchase #2	$29.71	5.830%	$31.4421	$31.44	$31.45	$31.40
Purchase #3	$79.38	13.568%	$90.1503	$90.15	$90.15	$90.20
Purchase #4	$102.40	9.374%	$111.999	$112.00	$112.00	$112.00
Purchase #5	$187.42	8.462%	$203.2795	$203.28	$203.30	$203.30
Purchase #6	$68.75	5.285%	$72.3834	$72.38	$72.40	$72.40
Purchase #7	$51.85	5.141%	$54.5156	$54.52	$54.50	$54.50
7 purchase totals =	$573.45		$623.7458	$623.75	$623.80	$623.80