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	$84.33	13.741%	$95.9178	$95.92	$95.90	$95.90
Purchase #2	$21.64	3.364%	$22.368	$22.37	$22.35	$22.40
Purchase #3	$99.44	10.404%	$109.7857	$109.79	$109.80	$109.80
Purchase #4	$7.79	9.353%	$8.5186	$8.52	$8.50	$8.50
Purchase #5	$51.59	9.162%	$56.3167	$56.32	$56.30	$56.30
Purchase #6	$137.88	12.464%	$155.0654	$155.07	$155.05	$155.10
Purchase #7	$119.78	10.679%	$132.5713	$132.57	$132.55	$132.60
7 purchase totals =	$522.45		$580.5435	$580.56	$580.45	$580.60