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	$40.60	10.220%	$44.7493	$44.75	$44.75	$44.70
Purchase #2	$211.44	11.813%	$236.4174	$236.42	$236.40	$236.40
Purchase #3	$193.71	9.196%	$211.5236	$211.52	$211.50	$211.50
Purchase #4	$152.32	8.608%	$165.4317	$165.43	$165.45	$165.40
Purchase #5	$70.43	10.857%	$78.0766	$78.08	$78.10	$78.10
Purchase #6	$117.89	7.238%	$126.4229	$126.42	$126.40	$126.40
Purchase #7	$40.81	10.517%	$45.102	$45.10	$45.10	$45.10
7 purchase totals =	$827.20		$907.7235	$907.72	$907.70	$907.60