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	$83.47	9.188%	$91.1392	$91.14	$91.15	$91.10
Purchase #2	$47.72	5.728%	$50.4534	$50.45	$50.45	$50.50
Purchase #3	$57.45	4.105%	$59.8083	$59.81	$59.80	$59.80
Purchase #4	$233.69	7.384%	$250.9457	$250.95	$250.95	$250.90
Purchase #5	$213.26	4.375%	$222.5901	$222.59	$222.60	$222.60
Purchase #6	$119.35	3.714%	$123.7827	$123.78	$123.80	$123.80
Purchase #7	$66.42	11.766%	$74.235	$74.24	$74.25	$74.20
7 purchase totals =	$821.36		$872.9544	$872.96	$873.00	$872.90