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	$41.46	12.352%	$46.5811	$46.58	$46.60	$46.60
Purchase #2	$43.75	8.123%	$47.3038	$47.30	$47.30	$47.30
Purchase #3	$215.32	9.545%	$235.8723	$235.87	$235.85	$235.90
Purchase #4	$167.45	7.382%	$179.8112	$179.81	$179.80	$179.80
Purchase #5	$53.37	8.707%	$58.0169	$58.02	$58.00	$58.00
Purchase #6	$66.95	6.820%	$71.516	$71.52	$71.50	$71.50
Purchase #7	$62.37	7.187%	$66.8525	$66.85	$66.85	$66.90
7 purchase totals =	$650.67		$705.9538	$705.95	$705.90	$706.00