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	$44.62	4.329%	$46.5516	$46.55	$46.55	$46.60
Purchase #2	$76.75	5.239%	$80.7709	$80.77	$80.75	$80.80
Purchase #3	$43.90	7.175%	$47.0498	$47.05	$47.05	$47.00
Purchase #4	$10.95	10.679%	$12.1194	$12.12	$12.10	$12.10
Purchase #5	$77.82	11.297%	$86.6113	$86.61	$86.60	$86.60
Purchase #6	$112.63	7.120%	$120.6493	$120.65	$120.65	$120.60
Purchase #7	$123.82	12.388%	$139.1588	$139.16	$139.15	$139.20
7 purchase totals =	$490.49		$532.9111	$532.91	$532.85	$532.90