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	$143.27	9.142%	$156.3677	$156.37	$156.35	$156.40
Purchase #2	$181.64	9.309%	$198.5489	$198.55	$198.55	$198.50
Purchase #3	$39.96	8.528%	$43.3678	$43.37	$43.35	$43.40
Purchase #4	$22.88	5.555%	$24.151	$24.15	$24.15	$24.20
Purchase #5	$92.38	13.583%	$104.928	$104.93	$104.95	$104.90
Purchase #6	$116.41	13.286%	$131.8762	$131.88	$131.90	$131.90
Purchase #7	$86.55	10.155%	$95.3392	$95.34	$95.35	$95.30
7 purchase totals =	$683.09		$754.5788	$754.59	$754.60	$754.60