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	$102.47	10.530%	$113.2601	$113.26	$113.25	$113.30
Purchase #2	$213.39	5.578%	$225.2929	$225.29	$225.30	$225.30
Purchase #3	$13.68	13.410%	$15.5145	$15.51	$15.50	$15.50
Purchase #4	$234.30	11.515%	$261.2796	$261.28	$261.30	$261.30
Purchase #5	$62.36	6.868%	$66.6429	$66.64	$66.65	$66.60
Purchase #6	$98.51	13.131%	$111.4453	$111.45	$111.45	$111.40
Purchase #7	$148.46	11.600%	$165.6814	$165.68	$165.70	$165.70
7 purchase totals =	$873.17		$959.1167	$959.11	$959.15	$959.10