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	$116.47	12.561%	$131.0998	$131.10	$131.10	$131.10
Purchase #2	$14.60	5.291%	$15.3725	$15.37	$15.35	$15.40
Purchase #3	$241.27	9.185%	$263.4306	$263.43	$263.45	$263.40
Purchase #4	$144.84	4.437%	$151.2666	$151.27	$151.25	$151.30
Purchase #5	$5.56	11.491%	$6.1989	$6.20	$6.20	$6.20
Purchase #6	$174.87	8.402%	$189.5626	$189.56	$189.55	$189.60
Purchase #7	$240.50	7.418%	$258.3403	$258.34	$258.35	$258.30
7 purchase totals =	$938.11		$1,015.2713	$1,015.27	$1,015.25	$1,015.30