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	$90.88	11.724%	$101.5348	$101.53	$101.55	$101.50
Purchase #2	$227.90	10.696%	$252.2762	$252.28	$252.30	$252.30
Purchase #3	$140.48	6.258%	$149.2712	$149.27	$149.25	$149.30
Purchase #4	$66.25	9.823%	$72.7577	$72.76	$72.75	$72.80
Purchase #5	$104.39	4.572%	$109.1627	$109.16	$109.15	$109.20
Purchase #6	$106.53	4.343%	$111.1566	$111.16	$111.15	$111.20
Purchase #7	$147.86	5.425%	$155.8814	$155.88	$155.90	$155.90
7 purchase totals =	$884.29		$952.0406	$952.04	$952.05	$952.20