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	$93.69	12.152%	$105.0752	$105.08	$105.10	$105.10
Purchase #2	$206.49	6.291%	$219.4803	$219.48	$219.50	$219.50
Purchase #3	$250.51	11.238%	$278.6623	$278.66	$278.65	$278.70
Purchase #4	$126.90	10.239%	$139.8933	$139.89	$139.90	$139.90
Purchase #5	$8.28	4.372%	$8.642	$8.64	$8.65	$8.60
Purchase #6	$101.90	10.655%	$112.7574	$112.76	$112.75	$112.80
Purchase #7	$88.37	13.484%	$100.2858	$100.29	$100.30	$100.30
7 purchase totals =	$876.14		$964.7963	$964.80	$964.85	$964.90