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	$41.96	4.651%	$43.9116	$43.91	$43.90	$43.90
Purchase #2	$100.96	11.574%	$112.6451	$112.65	$112.65	$112.60
Purchase #3	$76.27	11.828%	$85.2912	$85.29	$85.30	$85.30
Purchase #4	$90.34	12.821%	$101.9225	$101.92	$101.90	$101.90
Purchase #5	$51.71	10.550%	$57.1654	$57.17	$57.15	$57.20
Purchase #6	$220.80	4.374%	$230.4578	$230.46	$230.45	$230.50
Purchase #7	$120.92	9.673%	$132.6166	$132.62	$132.60	$132.60
7 purchase totals =	$702.96		$764.0102	$764.02	$763.95	$764.00