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	$92.25	4.648%	$96.5378	$96.54	$96.55	$96.50
Purchase #2	$5.88	4.197%	$6.1268	$6.13	$6.15	$6.10
Purchase #3	$177.34	6.395%	$188.6809	$188.68	$188.70	$188.70
Purchase #4	$146.38	12.660%	$164.9117	$164.91	$164.90	$164.90
Purchase #5	$41.92	9.445%	$45.8793	$45.88	$45.90	$45.90
Purchase #6	$149.32	11.341%	$166.2544	$166.25	$166.25	$166.30
Purchase #7	$36.93	13.791%	$42.023	$42.02	$42.00	$42.00
7 purchase totals =	$650.02		$710.4139	$710.41	$710.45	$710.40