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	$151.71	9.174%	$165.6279	$165.63	$165.65	$165.60
Purchase #2	$167.42	11.479%	$186.6381	$186.64	$186.65	$186.60
Purchase #3	$177.41	4.290%	$185.0209	$185.02	$185.00	$185.00
Purchase #4	$132.33	9.195%	$144.4977	$144.50	$144.50	$144.50
Purchase #5	$56.90	5.362%	$59.951	$59.95	$59.95	$60.00
Purchase #6	$11.72	7.464%	$12.5948	$12.59	$12.60	$12.60
Purchase #7	$250.62	5.852%	$265.2863	$265.29	$265.30	$265.30
7 purchase totals =	$948.11		$1,019.6167	$1,019.62	$1,019.65	$1,019.60