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	$237.72	7.870%	$256.4286	$256.43	$256.45	$256.40
Purchase #2	$95.46	8.183%	$103.2715	$103.27	$103.25	$103.30
Purchase #3	$32.56	3.228%	$33.611	$33.61	$33.60	$33.60
Purchase #4	$18.55	8.717%	$20.167	$20.17	$20.15	$20.20
Purchase #5	$27.88	4.540%	$29.1458	$29.15	$29.15	$29.10
Purchase #6	$61.67	7.861%	$66.5179	$66.52	$66.50	$66.50
Purchase #7	$41.74	13.375%	$47.3227	$47.32	$47.30	$47.30
7 purchase totals =	$515.58		$556.4645	$556.47	$556.40	$556.40