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	$146.91	9.184%	$160.4022	$160.40	$160.40	$160.40
Purchase #2	$172.46	13.167%	$195.1678	$195.17	$195.15	$195.20
Purchase #3	$171.87	5.536%	$181.3847	$181.38	$181.40	$181.40
Purchase #4	$170.37	4.832%	$178.6023	$178.60	$178.60	$178.60
Purchase #5	$135.49	11.737%	$151.3925	$151.39	$151.40	$151.40
Purchase #6	$231.46	5.115%	$243.2992	$243.30	$243.30	$243.30
Purchase #7	$50.56	10.478%	$55.8577	$55.86	$55.85	$55.90
7 purchase totals =	$1,079.12		$1,166.1064	$1,166.10	$1,166.10	$1,166.20