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	$179.28	10.565%	$198.2209	$198.22	$198.20	$198.20
Purchase #2	$213.26	4.341%	$222.5176	$222.52	$222.50	$222.50
Purchase #3	$188.75	13.231%	$213.7235	$213.72	$213.70	$213.70
Purchase #4	$118.60	11.379%	$132.0955	$132.10	$132.10	$132.10
Purchase #5	$169.67	9.506%	$185.7988	$185.80	$185.80	$185.80
Purchase #6	$11.53	5.358%	$12.1478	$12.15	$12.15	$12.10
Purchase #7	$73.45	7.366%	$78.8603	$78.86	$78.85	$78.90
7 purchase totals =	$954.54		$1,043.3644	$1,043.37	$1,043.30	$1,043.30