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	$30.38	6.847%	$32.4601	$32.46	$32.45	$32.50
Purchase #2	$227.40	12.363%	$255.5135	$255.51	$255.50	$255.50
Purchase #3	$202.74	5.262%	$213.4082	$213.41	$213.40	$213.40
Purchase #4	$122.26	8.720%	$132.9211	$132.92	$132.90	$132.90
Purchase #5	$40.67	10.839%	$45.0782	$45.08	$45.10	$45.10
Purchase #6	$106.46	9.256%	$116.3139	$116.31	$116.30	$116.30
Purchase #7	$246.28	6.839%	$263.1231	$263.12	$263.10	$263.10
7 purchase totals =	$976.19		$1,058.8181	$1,058.81	$1,058.75	$1,058.80