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	$141.30	5.354%	$148.8652	$148.87	$148.85	$148.90
Purchase #2	$134.46	8.163%	$145.436	$145.44	$145.45	$145.40
Purchase #3	$228.76	12.104%	$256.4491	$256.45	$256.45	$256.40
Purchase #4	$144.29	4.704%	$151.0774	$151.08	$151.10	$151.10
Purchase #5	$165.76	9.264%	$181.116	$181.12	$181.10	$181.10
Purchase #6	$64.85	5.740%	$68.5724	$68.57	$68.55	$68.60
Purchase #7	$175.73	8.312%	$190.3367	$190.34	$190.35	$190.30
7 purchase totals =	$1,055.15		$1,141.8528	$1,141.87	$1,141.85	$1,141.80