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	$51.27	13.846%	$58.3688	$58.37	$58.35	$58.40
Purchase #2	$71.49	10.214%	$78.792	$78.79	$78.80	$78.80
Purchase #3	$39.55	11.711%	$44.1817	$44.18	$44.20	$44.20
Purchase #4	$99.97	9.110%	$109.0773	$109.08	$109.10	$109.10
Purchase #5	$108.39	13.628%	$123.1614	$123.16	$123.15	$123.20
Purchase #6	$143.83	3.214%	$148.4527	$148.45	$148.45	$148.50
Purchase #7	$104.41	10.476%	$115.348	$115.35	$115.35	$115.30
7 purchase totals =	$618.91		$677.3819	$677.38	$677.40	$677.50