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	$140.78	11.253%	$156.622	$156.62	$156.60	$156.60
Purchase #2	$126.30	11.782%	$141.1807	$141.18	$141.20	$141.20
Purchase #3	$139.25	13.802%	$158.4693	$158.47	$158.45	$158.50
Purchase #4	$94.33	4.608%	$98.6767	$98.68	$98.70	$98.70
Purchase #5	$233.30	12.847%	$263.2721	$263.27	$263.25	$263.30
Purchase #6	$159.61	5.539%	$168.4508	$168.45	$168.45	$168.50
Purchase #7	$38.36	9.156%	$41.8722	$41.87	$41.85	$41.90
7 purchase totals =	$931.93		$1,028.5438	$1,028.54	$1,028.50	$1,028.70