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	$148.26	11.475%	$165.2728	$165.27	$165.25	$165.30
Purchase #2	$36.69	8.721%	$39.8897	$39.89	$39.90	$39.90
Purchase #3	$74.68	4.305%	$77.895	$77.90	$77.90	$77.90
Purchase #4	$56.56	6.729%	$60.3659	$60.37	$60.35	$60.40
Purchase #5	$57.43	9.499%	$62.8853	$62.89	$62.90	$62.90
Purchase #6	$114.60	10.385%	$126.5012	$126.50	$126.50	$126.50
Purchase #7	$168.68	12.451%	$189.6823	$189.68	$189.70	$189.70
7 purchase totals =	$656.90		$722.4922	$722.50	$722.50	$722.60