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	$153.36	6.755%	$163.7195	$163.72	$163.70	$163.70
Purchase #2	$139.98	3.779%	$145.2698	$145.27	$145.25	$145.30
Purchase #3	$209.87	4.634%	$219.5954	$219.60	$219.60	$219.60
Purchase #4	$160.87	8.651%	$174.7869	$174.79	$174.80	$174.80
Purchase #5	$112.82	13.258%	$127.7777	$127.78	$127.80	$127.80
Purchase #6	$78.51	12.741%	$88.513	$88.51	$88.50	$88.50
Purchase #7	$170.47	9.187%	$186.1311	$186.13	$186.15	$186.10
7 purchase totals =	$1,025.88		$1,105.7934	$1,105.80	$1,105.80	$1,105.80