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	$13.49	5.109%	$14.1792	$14.18	$14.20	$14.20
Purchase #2	$209.46	8.611%	$227.4966	$227.50	$227.50	$227.50
Purchase #3	$130.70	13.466%	$148.3001	$148.30	$148.30	$148.30
Purchase #4	$20.56	9.646%	$22.5432	$22.54	$22.55	$22.50
Purchase #5	$33.89	5.316%	$35.6916	$35.69	$35.70	$35.70
Purchase #6	$95.38	8.423%	$103.4139	$103.41	$103.40	$103.40
Purchase #7	$146.78	10.711%	$162.5016	$162.50	$162.50	$162.50
7 purchase totals =	$650.26		$714.1262	$714.12	$714.15	$714.10