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	$82.59	8.428%	$89.5507	$89.55	$89.55	$89.60
Purchase #2	$11.80	11.455%	$13.1517	$13.15	$13.15	$13.20
Purchase #3	$198.99	5.332%	$209.6001	$209.60	$209.60	$209.60
Purchase #4	$137.66	8.161%	$148.8944	$148.89	$148.90	$148.90
Purchase #5	$46.89	13.758%	$53.3411	$53.34	$53.35	$53.30
Purchase #6	$177.61	12.641%	$200.0617	$200.06	$200.05	$200.10
Purchase #7	$181.30	6.160%	$192.4681	$192.47	$192.45	$192.50
7 purchase totals =	$836.84		$907.0678	$907.06	$907.05	$907.20