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	$32.55	5.790%	$34.4346	$34.43	$34.45	$34.40
Purchase #2	$249.96	6.667%	$266.6248	$266.62	$266.60	$266.60
Purchase #3	$211.43	12.193%	$237.2097	$237.21	$237.20	$237.20
Purchase #4	$74.25	10.658%	$82.1636	$82.16	$82.15	$82.20
Purchase #5	$214.94	3.871%	$223.2603	$223.26	$223.25	$223.30
Purchase #6	$165.77	11.252%	$184.4224	$184.42	$184.40	$184.40
Purchase #7	$70.37	11.419%	$78.4056	$78.41	$78.40	$78.40
7 purchase totals =	$1,019.27		$1,106.5210	$1,106.51	$1,106.45	$1,106.50