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	$223.25	3.753%	$231.6286	$231.63	$231.65	$231.60
Purchase #2	$118.63	7.280%	$127.2663	$127.27	$127.25	$127.30
Purchase #3	$201.51	10.345%	$222.3562	$222.36	$222.35	$222.40
Purchase #4	$149.85	6.155%	$159.0733	$159.07	$159.05	$159.10
Purchase #5	$224.80	10.456%	$248.3051	$248.31	$248.30	$248.30
Purchase #6	$182.38	3.325%	$188.4441	$188.44	$188.45	$188.40
Purchase #7	$158.27	11.773%	$176.9031	$176.90	$176.90	$176.90
7 purchase totals =	$1,258.69		$1,353.9767	$1,353.98	$1,353.95	$1,354.00