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	$205.37	10.704%	$227.3528	$227.35	$227.35	$227.40
Purchase #2	$125.28	10.437%	$138.3555	$138.36	$138.35	$138.40
Purchase #3	$132.50	6.838%	$141.5604	$141.56	$141.55	$141.60
Purchase #4	$37.46	3.738%	$38.8603	$38.86	$38.85	$38.90
Purchase #5	$96.55	3.142%	$99.5836	$99.58	$99.60	$99.60
Purchase #6	$248.34	7.130%	$266.0466	$266.05	$266.05	$266.00
Purchase #7	$127.73	9.622%	$140.0202	$140.02	$140.00	$140.00
7 purchase totals =	$973.23		$1,051.7794	$1,051.78	$1,051.75	$1,051.90