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	$5.26	6.272%	$5.5899	$5.59	$5.60	$5.60
Purchase #2	$200.83	10.579%	$222.0758	$222.08	$222.10	$222.10
Purchase #3	$233.29	5.211%	$245.4467	$245.45	$245.45	$245.40
Purchase #4	$170.91	4.808%	$179.1274	$179.13	$179.15	$179.10
Purchase #5	$76.96	7.327%	$82.5989	$82.60	$82.60	$82.60
Purchase #6	$140.91	6.756%	$150.4299	$150.43	$150.45	$150.40
Purchase #7	$141.31	4.804%	$148.0985	$148.10	$148.10	$148.10
7 purchase totals =	$969.47		$1,033.3671	$1,033.38	$1,033.45	$1,033.30