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	$165.46	8.712%	$179.8749	$179.87	$179.85	$179.90
Purchase #2	$180.52	5.405%	$190.2771	$190.28	$190.30	$190.30
Purchase #3	$66.60	8.634%	$72.3502	$72.35	$72.35	$72.40
Purchase #4	$166.25	13.643%	$188.9315	$188.93	$188.95	$188.90
Purchase #5	$182.50	4.743%	$191.156	$191.16	$191.15	$191.20
Purchase #6	$111.85	4.495%	$116.8777	$116.88	$116.90	$116.90
Purchase #7	$103.45	3.651%	$107.227	$107.23	$107.25	$107.20
7 purchase totals =	$976.63		$1,046.6944	$1,046.70	$1,046.75	$1,046.80