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	$56.82	8.647%	$61.7332	$61.73	$61.75	$61.70
Purchase #2	$38.40	11.359%	$42.7619	$42.76	$42.75	$42.80
Purchase #3	$225.72	13.686%	$256.612	$256.61	$256.60	$256.60
Purchase #4	$60.47	12.253%	$67.8794	$67.88	$67.90	$67.90
Purchase #5	$212.33	13.634%	$241.2791	$241.28	$241.30	$241.30
Purchase #6	$131.79	4.712%	$137.9999	$138.00	$138.00	$138.00
Purchase #7	$47.35	9.840%	$52.0092	$52.01	$52.00	$52.00
7 purchase totals =	$772.88		$860.2747	$860.27	$860.30	$860.30