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	$158.78	10.589%	$175.5932	$175.59	$175.60	$175.60
Purchase #2	$153.60	7.476%	$165.0831	$165.08	$165.10	$165.10
Purchase #3	$41.78	13.346%	$47.356	$47.36	$47.35	$47.40
Purchase #4	$10.32	12.536%	$11.6137	$11.61	$11.60	$11.60
Purchase #5	$215.82	10.683%	$238.8761	$238.88	$238.90	$238.90
Purchase #6	$188.88	11.133%	$209.908	$209.91	$209.90	$209.90
Purchase #7	$32.39	4.206%	$33.7523	$33.75	$33.75	$33.80
7 purchase totals =	$801.57		$882.1824	$882.18	$882.20	$882.30