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	$114.88	10.606%	$127.0642	$127.06	$127.05	$127.10
Purchase #2	$40.30	7.678%	$43.3942	$43.39	$43.40	$43.40
Purchase #3	$57.70	6.182%	$61.267	$61.27	$61.25	$61.30
Purchase #4	$231.60	4.355%	$241.6862	$241.69	$241.70	$241.70
Purchase #5	$80.64	12.589%	$90.7918	$90.79	$90.80	$90.80
Purchase #6	$236.67	4.352%	$246.9699	$246.97	$246.95	$247.00
Purchase #7	$38.98	3.693%	$40.4195	$40.42	$40.40	$40.40
7 purchase totals =	$800.77		$851.5928	$851.59	$851.55	$851.70