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	$182.29	12.409%	$204.9104	$204.91	$204.90	$204.90
Purchase #2	$21.54	13.322%	$24.4096	$24.41	$24.40	$24.40
Purchase #3	$111.90	10.526%	$123.6786	$123.68	$123.70	$123.70
Purchase #4	$212.83	5.570%	$224.6846	$224.68	$224.70	$224.70
Purchase #5	$44.56	5.619%	$47.0638	$47.06	$47.05	$47.10
Purchase #6	$176.31	3.171%	$181.9008	$181.90	$181.90	$181.90
Purchase #7	$55.43	6.836%	$59.2192	$59.22	$59.20	$59.20
7 purchase totals =	$804.86		$865.8670	$865.86	$865.85	$865.90