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	$75.73	13.783%	$86.1679	$86.17	$86.15	$86.20
Purchase #2	$184.32	3.453%	$190.6846	$190.68	$190.70	$190.70
Purchase #3	$215.82	10.674%	$238.8566	$238.86	$238.85	$238.90
Purchase #4	$230.83	4.685%	$241.6444	$241.64	$241.65	$241.60
Purchase #5	$112.63	13.573%	$127.9173	$127.92	$127.90	$127.90
Purchase #6	$162.83	3.636%	$168.7505	$168.75	$168.75	$168.80
Purchase #7	$27.82	10.815%	$30.8287	$30.83	$30.85	$30.80
7 purchase totals =	$1,009.98		$1,084.8500	$1,084.85	$1,084.85	$1,084.90