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	$110.39	8.339%	$119.5954	$119.60	$119.60	$119.60
Purchase #2	$177.61	4.782%	$186.1033	$186.10	$186.10	$186.10
Purchase #3	$133.52	8.627%	$145.0388	$145.04	$145.05	$145.00
Purchase #4	$13.89	10.197%	$15.3064	$15.31	$15.30	$15.30
Purchase #5	$72.78	7.608%	$78.3171	$78.32	$78.30	$78.30
Purchase #6	$20.58	7.642%	$22.1527	$22.15	$22.15	$22.20
Purchase #7	$174.45	7.493%	$187.5215	$187.52	$187.50	$187.50
7 purchase totals =	$703.22		$754.0352	$754.04	$754.00	$754.00