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	$114.69	4.298%	$119.6194	$119.62	$119.60	$119.60
Purchase #2	$119.86	11.453%	$133.5876	$133.59	$133.60	$133.60
Purchase #3	$105.50	9.808%	$115.8474	$115.85	$115.85	$115.80
Purchase #4	$149.82	11.793%	$167.4883	$167.49	$167.50	$167.50
Purchase #5	$61.97	5.675%	$65.4868	$65.49	$65.50	$65.50
Purchase #6	$250.59	12.766%	$282.5803	$282.58	$282.60	$282.60
Purchase #7	$62.64	13.540%	$71.1215	$71.12	$71.10	$71.10
7 purchase totals =	$865.07		$955.7313	$955.74	$955.75	$955.70