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	$91.25	3.428%	$94.3781	$94.38	$94.40	$94.40
Purchase #2	$96.44	8.247%	$104.3934	$104.39	$104.40	$104.40
Purchase #3	$144.30	8.576%	$156.6752	$156.68	$156.70	$156.70
Purchase #4	$103.82	8.241%	$112.3758	$112.38	$112.40	$112.40
Purchase #5	$32.94	7.844%	$35.5238	$35.52	$35.50	$35.50
Purchase #6	$122.91	4.149%	$128.0095	$128.01	$128.00	$128.00
Purchase #7	$205.94	10.469%	$227.4999	$227.50	$227.50	$227.50
7 purchase totals =	$797.60		$858.8557	$858.86	$858.90	$858.90