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	$176.56	10.704%	$195.459	$195.46	$195.45	$195.50
Purchase #2	$14.90	10.543%	$16.4709	$16.47	$16.45	$16.50
Purchase #3	$61.55	5.417%	$64.8842	$64.88	$64.90	$64.90
Purchase #4	$79.52	13.806%	$90.4985	$90.50	$90.50	$90.50
Purchase #5	$81.78	9.805%	$89.7985	$89.80	$89.80	$89.80
Purchase #6	$175.89	3.351%	$181.7841	$181.78	$181.80	$181.80
Purchase #7	$235.38	10.494%	$260.0808	$260.08	$260.10	$260.10
7 purchase totals =	$825.58		$898.9760	$898.97	$899.00	$899.10