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	$159.39	7.640%	$171.5674	$171.57	$171.55	$171.60
Purchase #2	$17.32	3.351%	$17.9004	$17.90	$17.90	$17.90
Purchase #3	$184.82	3.523%	$191.3312	$191.33	$191.35	$191.30
Purchase #4	$249.52	10.666%	$276.1338	$276.13	$276.15	$276.10
Purchase #5	$54.89	6.457%	$58.4342	$58.43	$58.45	$58.40
Purchase #6	$42.59	8.397%	$46.1663	$46.17	$46.15	$46.20
Purchase #7	$21.50	5.105%	$22.5976	$22.60	$22.60	$22.60
7 purchase totals =	$730.03		$784.1309	$784.13	$784.15	$784.10