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	$213.42	5.521%	$225.2029	$225.20	$225.20	$225.20
Purchase #2	$143.60	4.677%	$150.3162	$150.32	$150.30	$150.30
Purchase #3	$183.52	12.584%	$206.6142	$206.61	$206.60	$206.60
Purchase #4	$155.90	11.832%	$174.3461	$174.35	$174.35	$174.30
Purchase #5	$131.51	8.469%	$142.6476	$142.65	$142.65	$142.60
Purchase #6	$106.89	8.582%	$116.0633	$116.06	$116.05	$116.10
Purchase #7	$105.70	3.672%	$109.5813	$109.58	$109.60	$109.60
7 purchase totals =	$1,040.54		$1,124.7716	$1,124.77	$1,124.75	$1,124.70