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	$193.26	11.147%	$214.8027	$214.80	$214.80	$214.80
Purchase #2	$104.80	12.648%	$118.0551	$118.06	$118.05	$118.10
Purchase #3	$127.94	11.622%	$142.8092	$142.81	$142.80	$142.80
Purchase #4	$250.64	4.163%	$261.0741	$261.07	$261.05	$261.10
Purchase #5	$99.31	13.240%	$112.4586	$112.46	$112.45	$112.50
Purchase #6	$152.58	12.841%	$172.1728	$172.17	$172.15	$172.20
Purchase #7	$187.36	7.263%	$200.968	$200.97	$200.95	$201.00
7 purchase totals =	$1,115.89		$1,222.3405	$1,222.34	$1,222.25	$1,222.50