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	$132.94	6.715%	$141.8669	$141.87	$141.85	$141.90
Purchase #2	$192.47	12.493%	$216.5153	$216.52	$216.50	$216.50
Purchase #3	$51.68	11.644%	$57.6976	$57.70	$57.70	$57.70
Purchase #4	$179.91	6.656%	$191.8848	$191.88	$191.90	$191.90
Purchase #5	$151.67	5.214%	$159.5781	$159.58	$159.60	$159.60
Purchase #6	$127.51	11.721%	$142.4554	$142.46	$142.45	$142.50
Purchase #7	$35.74	9.481%	$39.1285	$39.13	$39.15	$39.10
7 purchase totals =	$871.92		$949.1266	$949.14	$949.15	$949.20