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	$248.52	8.592%	$269.8728	$269.87	$269.85	$269.90
Purchase #2	$234.40	8.868%	$255.1866	$255.19	$255.20	$255.20
Purchase #3	$211.74	4.531%	$221.3339	$221.33	$221.35	$221.30
Purchase #4	$69.71	13.175%	$78.8943	$78.89	$78.90	$78.90
Purchase #5	$42.90	8.675%	$46.6216	$46.62	$46.60	$46.60
Purchase #6	$101.46	8.507%	$110.0912	$110.09	$110.10	$110.10
Purchase #7	$153.59	10.338%	$169.4681	$169.47	$169.45	$169.50
7 purchase totals =	$1,062.32		$1,151.4685	$1,151.46	$1,151.45	$1,151.50