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	$176.31	12.136%	$197.707	$197.71	$197.70	$197.70
Purchase #2	$107.79	3.338%	$111.388	$111.39	$111.40	$111.40
Purchase #3	$151.36	7.360%	$162.5001	$162.50	$162.50	$162.50
Purchase #4	$101.58	6.152%	$107.8292	$107.83	$107.85	$107.80
Purchase #5	$170.42	12.552%	$191.8111	$191.81	$191.80	$191.80
Purchase #6	$168.51	10.622%	$186.4091	$186.41	$186.40	$186.40
Purchase #7	$126.83	7.702%	$136.5984	$136.60	$136.60	$136.60
7 purchase totals =	$1,002.80		$1,094.2429	$1,094.25	$1,094.25	$1,094.20