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	$233.70	10.203%	$257.5444	$257.54	$257.55	$257.50
Purchase #2	$70.61	8.803%	$76.8258	$76.83	$76.85	$76.80
Purchase #3	$168.34	6.531%	$179.3343	$179.33	$179.35	$179.30
Purchase #4	$156.30	6.452%	$166.3845	$166.38	$166.40	$166.40
Purchase #5	$199.97	11.177%	$222.3206	$222.32	$222.30	$222.30
Purchase #6	$49.94	10.185%	$55.0264	$55.03	$55.05	$55.00
Purchase #7	$118.36	7.843%	$127.643	$127.64	$127.65	$127.60
7 purchase totals =	$997.22		$1,085.0790	$1,085.07	$1,085.15	$1,084.90