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	$118.83	7.229%	$127.4202	$127.42	$127.40	$127.40
Purchase #2	$187.48	13.289%	$212.3942	$212.39	$212.40	$212.40
Purchase #3	$20.67	5.623%	$21.8323	$21.83	$21.85	$21.80
Purchase #4	$80.67	11.719%	$90.1237	$90.12	$90.10	$90.10
Purchase #5	$148.86	11.474%	$165.9402	$165.94	$165.95	$165.90
Purchase #6	$173.25	3.126%	$178.6658	$178.67	$178.65	$178.70
Purchase #7	$216.72	6.475%	$230.7526	$230.75	$230.75	$230.80
7 purchase totals =	$946.48		$1,027.1290	$1,027.12	$1,027.10	$1,027.10