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	$216.61	8.155%	$234.2745	$234.27	$234.25	$234.30
Purchase #2	$48.88	9.522%	$53.5344	$53.53	$53.55	$53.50
Purchase #3	$5.57	11.682%	$6.2207	$6.22	$6.20	$6.20
Purchase #4	$28.78	8.523%	$31.2329	$31.23	$31.25	$31.20
Purchase #5	$65.71	9.292%	$71.8158	$71.82	$71.80	$71.80
Purchase #6	$169.62	5.142%	$178.3419	$178.34	$178.35	$178.30
Purchase #7	$53.55	4.306%	$55.8559	$55.86	$55.85	$55.90
7 purchase totals =	$588.72		$631.2761	$631.27	$631.25	$631.20