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	$179.90	10.212%	$198.2714	$198.27	$198.25	$198.30
Purchase #2	$36.38	12.365%	$40.8784	$40.88	$40.90	$40.90
Purchase #3	$205.70	6.418%	$218.9018	$218.90	$218.90	$218.90
Purchase #4	$106.92	10.837%	$118.5069	$118.51	$118.50	$118.50
Purchase #5	$46.77	13.842%	$53.2439	$53.24	$53.25	$53.20
Purchase #6	$41.94	3.393%	$43.363	$43.36	$43.35	$43.40
Purchase #7	$36.91	10.873%	$40.9232	$40.92	$40.90	$40.90
7 purchase totals =	$654.52		$714.0886	$714.08	$714.05	$714.10