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	$81.77	12.328%	$91.8506	$91.85	$91.85	$91.90
Purchase #2	$63.96	13.778%	$72.7724	$72.77	$72.75	$72.80
Purchase #3	$11.53	6.694%	$12.3018	$12.30	$12.30	$12.30
Purchase #4	$215.26	6.154%	$228.5071	$228.51	$228.50	$228.50
Purchase #5	$230.43	11.339%	$256.5585	$256.56	$256.55	$256.60
Purchase #6	$224.42	10.758%	$248.5631	$248.56	$248.55	$248.60
Purchase #7	$99.43	12.229%	$111.5893	$111.59	$111.60	$111.60
7 purchase totals =	$926.80		$1,022.1428	$1,022.14	$1,022.10	$1,022.30