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	$90.48	6.623%	$96.4725	$96.47	$96.45	$96.50
Purchase #2	$41.84	4.795%	$43.8462	$43.85	$43.85	$43.80
Purchase #3	$90.39	12.156%	$101.3778	$101.38	$101.40	$101.40
Purchase #4	$150.68	3.712%	$156.2732	$156.27	$156.25	$156.30
Purchase #5	$219.93	11.357%	$244.9075	$244.91	$244.90	$244.90
Purchase #6	$217.44	4.826%	$227.9337	$227.93	$227.95	$227.90
Purchase #7	$45.50	9.499%	$49.822	$49.82	$49.80	$49.80
7 purchase totals =	$856.26		$920.6329	$920.63	$920.60	$920.60