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	$230.94	13.597%	$262.3409	$262.34	$262.35	$262.30
Purchase #2	$156.86	13.160%	$177.5028	$177.50	$177.50	$177.50
Purchase #3	$100.90	10.289%	$111.2816	$111.28	$111.30	$111.30
Purchase #4	$101.96	9.565%	$111.7125	$111.71	$111.70	$111.70
Purchase #5	$29.83	4.808%	$31.2642	$31.26	$31.25	$31.30
Purchase #6	$83.79	13.572%	$95.162	$95.16	$95.15	$95.20
Purchase #7	$32.97	13.213%	$37.3263	$37.33	$37.35	$37.30
7 purchase totals =	$737.25		$826.5903	$826.58	$826.60	$826.60