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	$161.79	6.578%	$172.4325	$172.43	$172.45	$172.40
Purchase #2	$228.50	11.708%	$255.2528	$255.25	$255.25	$255.30
Purchase #3	$52.81	13.247%	$59.8057	$59.81	$59.80	$59.80
Purchase #4	$29.65	9.482%	$32.4614	$32.46	$32.45	$32.50
Purchase #5	$50.81	8.582%	$55.1705	$55.17	$55.15	$55.20
Purchase #6	$223.87	9.146%	$244.3452	$244.35	$244.35	$244.30
Purchase #7	$242.72	6.758%	$259.123	$259.12	$259.10	$259.10
7 purchase totals =	$990.15		$1,078.5911	$1,078.59	$1,078.55	$1,078.60