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	$176.77	11.356%	$196.844	$196.84	$196.85	$196.80
Purchase #2	$234.83	12.644%	$264.5219	$264.52	$264.50	$264.50
Purchase #3	$29.61	11.726%	$33.0821	$33.08	$33.10	$33.10
Purchase #4	$73.78	10.104%	$81.2347	$81.23	$81.25	$81.20
Purchase #5	$60.94	4.175%	$63.4842	$63.48	$63.50	$63.50
Purchase #6	$50.47	13.585%	$57.3263	$57.33	$57.35	$57.30
Purchase #7	$153.92	11.140%	$171.0667	$171.07	$171.05	$171.10
7 purchase totals =	$780.32		$867.5599	$867.55	$867.60	$867.50