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	$218.49	10.849%	$242.194	$242.19	$242.20	$242.20
Purchase #2	$176.52	11.304%	$196.4738	$196.47	$196.45	$196.50
Purchase #3	$230.91	10.542%	$255.2525	$255.25	$255.25	$255.30
Purchase #4	$188.96	10.243%	$208.3152	$208.32	$208.30	$208.30
Purchase #5	$156.98	4.364%	$163.8306	$163.83	$163.85	$163.80
Purchase #6	$56.26	3.783%	$58.3883	$58.39	$58.40	$58.40
Purchase #7	$55.48	9.209%	$60.5892	$60.59	$60.60	$60.60
7 purchase totals =	$1,083.60		$1,185.0436	$1,185.04	$1,185.05	$1,185.10