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	$181.40	13.177%	$205.3031	$205.30	$205.30	$205.30
Purchase #2	$102.71	11.341%	$114.3583	$114.36	$114.35	$114.40
Purchase #3	$231.72	3.777%	$240.4721	$240.47	$240.45	$240.50
Purchase #4	$241.39	8.316%	$261.464	$261.46	$261.45	$261.50
Purchase #5	$56.35	10.470%	$62.2498	$62.25	$62.25	$62.20
Purchase #6	$123.77	8.820%	$134.6865	$134.69	$134.70	$134.70
Purchase #7	$59.39	13.797%	$67.584	$67.58	$67.60	$67.60
7 purchase totals =	$996.73		$1,086.1178	$1,086.11	$1,086.10	$1,086.20