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	$112.39	10.851%	$124.5854	$124.59	$124.60	$124.60
Purchase #2	$127.51	3.382%	$131.8224	$131.82	$131.80	$131.80
Purchase #3	$133.98	5.828%	$141.7884	$141.79	$141.80	$141.80
Purchase #4	$93.66	10.172%	$103.1871	$103.19	$103.20	$103.20
Purchase #5	$104.44	7.613%	$112.391	$112.39	$112.40	$112.40
Purchase #6	$13.39	7.283%	$14.3652	$14.37	$14.35	$14.40
Purchase #7	$34.92	11.415%	$38.9061	$38.91	$38.90	$38.90
7 purchase totals =	$620.29		$667.0456	$667.06	$667.05	$667.10