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	$220.32	10.607%	$243.6893	$243.69	$243.70	$243.70
Purchase #2	$33.96	11.105%	$37.7313	$37.73	$37.75	$37.70
Purchase #3	$118.99	12.163%	$133.4628	$133.46	$133.45	$133.50
Purchase #4	$152.30	4.154%	$158.6265	$158.63	$158.65	$158.60
Purchase #5	$87.32	4.138%	$90.9333	$90.93	$90.95	$90.90
Purchase #6	$152.96	10.675%	$169.2885	$169.29	$169.30	$169.30
Purchase #7	$35.86	10.720%	$39.7042	$39.70	$39.70	$39.70
7 purchase totals =	$801.71		$873.4359	$873.43	$873.50	$873.40