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	$40.48	7.348%	$43.4545	$43.45	$43.45	$43.50
Purchase #2	$236.36	10.869%	$262.05	$262.05	$262.05	$262.10
Purchase #3	$184.27	3.499%	$190.7176	$190.72	$190.70	$190.70
Purchase #4	$220.73	5.269%	$232.3603	$232.36	$232.35	$232.40
Purchase #5	$177.52	4.466%	$185.448	$185.45	$185.45	$185.40
Purchase #6	$50.42	13.298%	$57.1249	$57.12	$57.10	$57.10
Purchase #7	$241.81	6.704%	$258.0209	$258.02	$258.00	$258.00
7 purchase totals =	$1,151.59		$1,229.1762	$1,229.17	$1,229.10	$1,229.20