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	$113.41	12.253%	$127.3061	$127.31	$127.30	$127.30
Purchase #2	$197.81	10.435%	$218.4515	$218.45	$218.45	$218.50
Purchase #3	$37.94	11.721%	$42.3869	$42.39	$42.40	$42.40
Purchase #4	$183.29	7.822%	$197.6269	$197.63	$197.65	$197.60
Purchase #5	$154.89	13.577%	$175.9194	$175.92	$175.90	$175.90
Purchase #6	$145.92	6.262%	$155.0575	$155.06	$155.05	$155.10
Purchase #7	$224.78	13.870%	$255.957	$255.96	$255.95	$256.00
7 purchase totals =	$1,058.04		$1,172.7053	$1,172.72	$1,172.70	$1,172.80