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	$65.92	9.648%	$72.28	$72.28	$72.30	$72.30
Purchase #2	$162.75	10.784%	$180.301	$180.30	$180.30	$180.30
Purchase #3	$145.45	12.836%	$164.12	$164.12	$164.10	$164.10
Purchase #4	$172.97	8.579%	$187.8091	$187.81	$187.80	$187.80
Purchase #5	$38.90	12.141%	$43.6228	$43.62	$43.60	$43.60
Purchase #6	$130.41	13.572%	$148.1092	$148.11	$148.10	$148.10
Purchase #7	$158.70	6.714%	$169.3551	$169.36	$169.35	$169.40
7 purchase totals =	$875.10		$965.5972	$965.60	$965.55	$965.60