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	$45.34	11.721%	$50.6543	$50.65	$50.65	$50.70
Purchase #2	$91.60	8.587%	$99.4657	$99.47	$99.45	$99.50
Purchase #3	$17.34	10.453%	$19.1526	$19.15	$19.15	$19.20
Purchase #4	$171.77	3.680%	$178.0911	$178.09	$178.10	$178.10
Purchase #5	$56.53	12.433%	$63.5584	$63.56	$63.55	$63.60
Purchase #6	$248.94	4.180%	$259.3457	$259.35	$259.35	$259.30
Purchase #7	$224.69	13.738%	$255.5579	$255.56	$255.55	$255.60
7 purchase totals =	$856.21		$925.8257	$925.83	$925.80	$926.00