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	$79.53	10.475%	$87.8608	$87.86	$87.85	$87.90
Purchase #2	$104.65	10.162%	$115.2845	$115.28	$115.30	$115.30
Purchase #3	$40.59	6.709%	$43.3132	$43.31	$43.30	$43.30
Purchase #4	$34.47	10.713%	$38.1628	$38.16	$38.15	$38.20
Purchase #5	$130.42	8.771%	$141.8591	$141.86	$141.85	$141.90
Purchase #6	$200.96	13.398%	$227.8846	$227.88	$227.90	$227.90
Purchase #7	$37.26	3.647%	$38.6189	$38.62	$38.60	$38.60
7 purchase totals =	$627.88		$692.9839	$692.97	$692.95	$693.10