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	$106.48	7.497%	$114.4628	$114.46	$114.45	$114.50
Purchase #2	$158.29	11.518%	$176.5218	$176.52	$176.50	$176.50
Purchase #3	$100.71	4.578%	$105.3205	$105.32	$105.30	$105.30
Purchase #4	$36.27	6.797%	$38.7353	$38.74	$38.75	$38.70
Purchase #5	$162.86	12.860%	$183.8038	$183.80	$183.80	$183.80
Purchase #6	$48.77	6.279%	$51.8323	$51.83	$51.85	$51.80
Purchase #7	$116.74	9.858%	$128.2482	$128.25	$128.25	$128.20
7 purchase totals =	$730.12		$798.9247	$798.92	$798.90	$798.80