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	$173.60	5.686%	$183.4709	$183.47	$183.45	$183.50
Purchase #2	$100.37	10.666%	$111.0755	$111.08	$111.10	$111.10
Purchase #3	$19.47	5.107%	$20.4643	$20.46	$20.45	$20.50
Purchase #4	$181.56	13.398%	$205.8854	$205.89	$205.90	$205.90
Purchase #5	$204.57	6.662%	$218.1985	$218.20	$218.20	$218.20
Purchase #6	$79.27	8.298%	$85.8478	$85.85	$85.85	$85.80
Purchase #7	$197.68	11.426%	$220.2669	$220.27	$220.25	$220.30
7 purchase totals =	$956.52		$1,045.2093	$1,045.22	$1,045.20	$1,045.30