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	$158.51	12.545%	$178.3951	$178.40	$178.40	$178.40
Purchase #2	$136.67	12.859%	$154.2444	$154.24	$154.25	$154.20
Purchase #3	$24.54	10.578%	$27.1358	$27.14	$27.15	$27.10
Purchase #4	$159.82	9.111%	$174.3812	$174.38	$174.40	$174.40
Purchase #5	$31.55	5.563%	$33.3051	$33.31	$33.30	$33.30
Purchase #6	$39.29	6.522%	$41.8525	$41.85	$41.85	$41.90
Purchase #7	$78.85	8.782%	$85.7746	$85.77	$85.75	$85.80
7 purchase totals =	$629.23		$695.0887	$695.09	$695.10	$695.10