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	$149.81	10.553%	$165.6194	$165.62	$165.60	$165.60
Purchase #2	$141.30	6.552%	$150.558	$150.56	$150.55	$150.60
Purchase #3	$96.94	7.303%	$104.0195	$104.02	$104.00	$104.00
Purchase #4	$141.25	6.289%	$150.1332	$150.13	$150.15	$150.10
Purchase #5	$120.30	9.861%	$132.1628	$132.16	$132.15	$132.20
Purchase #6	$29.29	13.128%	$33.1352	$33.14	$33.15	$33.10
Purchase #7	$61.61	6.397%	$65.5512	$65.55	$65.55	$65.60
7 purchase totals =	$740.50		$801.1793	$801.18	$801.15	$801.20