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	$247.98	5.368%	$261.2916	$261.29	$261.30	$261.30
Purchase #2	$49.82	6.321%	$52.9691	$52.97	$52.95	$53.00
Purchase #3	$28.70	13.371%	$32.5375	$32.54	$32.55	$32.50
Purchase #4	$115.31	10.869%	$127.843	$127.84	$127.85	$127.80
Purchase #5	$38.86	9.763%	$42.6539	$42.65	$42.65	$42.70
Purchase #6	$10.43	10.790%	$11.5554	$11.56	$11.55	$11.60
Purchase #7	$86.95	12.276%	$97.624	$97.62	$97.60	$97.60
7 purchase totals =	$578.05		$626.4745	$626.47	$626.45	$626.50