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	$223.69	9.720%	$245.4327	$245.43	$245.45	$245.40
Purchase #2	$148.31	12.114%	$166.2763	$166.28	$166.30	$166.30
Purchase #3	$142.90	12.135%	$160.2409	$160.24	$160.25	$160.20
Purchase #4	$70.50	11.598%	$78.6766	$78.68	$78.70	$78.70
Purchase #5	$169.30	12.746%	$190.879	$190.88	$190.90	$190.90
Purchase #6	$180.32	5.722%	$190.6379	$190.64	$190.65	$190.60
Purchase #7	$247.94	7.226%	$265.8561	$265.86	$265.85	$265.90
7 purchase totals =	$1,182.96		$1,297.9995	$1,298.01	$1,298.10	$1,298.00