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	$192.82	12.642%	$217.1963	$217.20	$217.20	$217.20
Purchase #2	$208.25	13.450%	$236.2596	$236.26	$236.25	$236.30
Purchase #3	$149.41	8.513%	$162.1293	$162.13	$162.15	$162.10
Purchase #4	$191.89	8.643%	$208.4751	$208.48	$208.50	$208.50
Purchase #5	$103.70	12.562%	$116.7268	$116.73	$116.75	$116.70
Purchase #6	$185.72	4.780%	$194.5974	$194.60	$194.60	$194.60
Purchase #7	$13.60	9.256%	$14.8588	$14.86	$14.85	$14.90
7 purchase totals =	$1,045.39		$1,150.2433	$1,150.26	$1,150.30	$1,150.30