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	$38.68	12.253%	$43.4195	$43.42	$43.40	$43.40
Purchase #2	$43.43	9.594%	$47.5967	$47.60	$47.60	$47.60
Purchase #3	$113.88	9.335%	$124.5107	$124.51	$124.50	$124.50
Purchase #4	$21.70	8.811%	$23.612	$23.61	$23.60	$23.60
Purchase #5	$57.40	5.194%	$60.3814	$60.38	$60.40	$60.40
Purchase #6	$229.31	5.588%	$242.1238	$242.12	$242.10	$242.10
Purchase #7	$56.78	5.482%	$59.8927	$59.89	$59.90	$59.90
7 purchase totals =	$561.18		$601.5368	$601.53	$601.50	$601.50