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	$237.70	10.839%	$263.4643	$263.46	$263.45	$263.50
Purchase #2	$51.58	11.536%	$57.5303	$57.53	$57.55	$57.50
Purchase #3	$124.30	10.861%	$137.8002	$137.80	$137.80	$137.80
Purchase #4	$34.69	13.384%	$39.3329	$39.33	$39.35	$39.30
Purchase #5	$36.32	13.290%	$41.1469	$41.15	$41.15	$41.10
Purchase #6	$103.81	5.254%	$109.2642	$109.26	$109.25	$109.30
Purchase #7	$200.55	11.126%	$222.8632	$222.86	$222.85	$222.90
7 purchase totals =	$788.95		$871.4020	$871.39	$871.40	$871.40