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	$167.94	13.844%	$191.1896	$191.19	$191.20	$191.20
Purchase #2	$55.80	7.426%	$59.9437	$59.94	$59.95	$59.90
Purchase #3	$111.41	13.446%	$126.3902	$126.39	$126.40	$126.40
Purchase #4	$218.61	13.849%	$248.8853	$248.89	$248.90	$248.90
Purchase #5	$73.55	9.582%	$80.5976	$80.60	$80.60	$80.60
Purchase #6	$121.35	10.703%	$134.3381	$134.34	$134.35	$134.30
Purchase #7	$162.92	6.375%	$173.3062	$173.31	$173.30	$173.30
7 purchase totals =	$911.58		$1,014.6507	$1,014.66	$1,014.70	$1,014.60