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	$130.60	13.784%	$148.6019	$148.60	$148.60	$148.60
Purchase #2	$137.33	9.646%	$150.5769	$150.58	$150.60	$150.60
Purchase #3	$116.73	12.832%	$131.7088	$131.71	$131.70	$131.70
Purchase #4	$66.83	11.181%	$74.3023	$74.30	$74.30	$74.30
Purchase #5	$114.71	10.780%	$127.0757	$127.08	$127.10	$127.10
Purchase #6	$76.31	6.463%	$81.2419	$81.24	$81.25	$81.20
Purchase #7	$9.94	3.501%	$10.288	$10.29	$10.30	$10.30
7 purchase totals =	$652.45		$723.7955	$723.80	$723.85	$723.80