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	$80.57	6.520%	$85.8232	$85.82	$85.80	$85.80
Purchase #2	$131.71	4.505%	$137.6435	$137.64	$137.65	$137.60
Purchase #3	$198.70	9.856%	$218.2839	$218.28	$218.30	$218.30
Purchase #4	$121.33	12.321%	$136.2791	$136.28	$136.30	$136.30
Purchase #5	$132.87	9.245%	$145.1538	$145.15	$145.15	$145.20
Purchase #6	$10.40	7.183%	$11.147	$11.15	$11.15	$11.10
Purchase #7	$83.75	8.838%	$91.1518	$91.15	$91.15	$91.20
7 purchase totals =	$759.33		$825.4823	$825.47	$825.50	$825.50