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	$137.73	5.620%	$145.4704	$145.47	$145.45	$145.50
Purchase #2	$232.56	4.476%	$242.9694	$242.97	$242.95	$243.00
Purchase #3	$38.55	10.507%	$42.6004	$42.60	$42.60	$42.60
Purchase #4	$88.47	13.655%	$100.5506	$100.55	$100.55	$100.60
Purchase #5	$180.82	5.469%	$190.709	$190.71	$190.70	$190.70
Purchase #6	$165.70	4.527%	$173.2012	$173.20	$173.20	$173.20
Purchase #7	$176.86	3.417%	$182.9033	$182.90	$182.90	$182.90
7 purchase totals =	$1,020.69		$1,078.4043	$1,078.40	$1,078.35	$1,078.50