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	$132.58	12.178%	$148.7256	$148.73	$148.75	$148.70
Purchase #2	$249.56	8.696%	$271.2617	$271.26	$271.25	$271.30
Purchase #3	$23.86	5.406%	$25.1499	$25.15	$25.15	$25.10
Purchase #4	$109.44	13.158%	$123.8401	$123.84	$123.85	$123.80
Purchase #5	$127.38	13.446%	$144.5075	$144.51	$144.50	$144.50
Purchase #6	$212.75	8.812%	$231.4975	$231.50	$231.50	$231.50
Purchase #7	$92.61	8.605%	$100.5791	$100.58	$100.60	$100.60
7 purchase totals =	$948.18		$1,045.5614	$1,045.57	$1,045.60	$1,045.50