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	$231.82	7.156%	$248.409	$248.41	$248.40	$248.40
Purchase #2	$17.82	13.131%	$20.1599	$20.16	$20.15	$20.20
Purchase #3	$130.86	12.270%	$146.9165	$146.92	$146.90	$146.90
Purchase #4	$154.94	6.440%	$164.9181	$164.92	$164.90	$164.90
Purchase #5	$82.68	10.809%	$91.6169	$91.62	$91.60	$91.60
Purchase #6	$169.25	10.160%	$186.4458	$186.45	$186.45	$186.40
Purchase #7	$40.78	5.612%	$43.0686	$43.07	$43.05	$43.10
7 purchase totals =	$828.15		$901.5348	$901.55	$901.45	$901.50