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	$59.96	13.599%	$68.114	$68.11	$68.10	$68.10
Purchase #2	$161.97	3.429%	$167.524	$167.52	$167.50	$167.50
Purchase #3	$48.91	9.359%	$53.4875	$53.49	$53.50	$53.50
Purchase #4	$250.88	9.856%	$275.6067	$275.61	$275.60	$275.60
Purchase #5	$206.25	5.305%	$217.1916	$217.19	$217.20	$217.20
Purchase #6	$50.83	9.592%	$55.7056	$55.71	$55.70	$55.70
Purchase #7	$238.76	11.194%	$265.4868	$265.49	$265.50	$265.50
7 purchase totals =	$1,017.56		$1,103.1162	$1,103.12	$1,103.10	$1,103.10