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	$189.36	3.243%	$195.5009	$195.50	$195.50	$195.50
Purchase #2	$198.32	3.389%	$205.0411	$205.04	$205.05	$205.00
Purchase #3	$229.55	11.496%	$255.9391	$255.94	$255.95	$255.90
Purchase #4	$62.72	10.565%	$69.3464	$69.35	$69.35	$69.30
Purchase #5	$143.46	13.242%	$162.457	$162.46	$162.45	$162.50
Purchase #6	$117.36	9.648%	$128.6829	$128.68	$128.70	$128.70
Purchase #7	$48.82	12.584%	$54.9635	$54.96	$54.95	$55.00
7 purchase totals =	$989.59		$1,071.9309	$1,071.93	$1,071.95	$1,071.90