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	$72.80	12.778%	$82.1024	$82.10	$82.10	$82.10
Purchase #2	$248.32	10.179%	$273.5965	$273.60	$273.60	$273.60
Purchase #3	$232.64	9.852%	$255.5597	$255.56	$255.55	$255.60
Purchase #4	$191.68	11.162%	$213.0753	$213.08	$213.10	$213.10
Purchase #5	$79.88	10.239%	$88.0589	$88.06	$88.05	$88.10
Purchase #6	$41.64	11.554%	$46.4511	$46.45	$46.45	$46.50
Purchase #7	$71.71	4.149%	$74.6852	$74.69	$74.70	$74.70
7 purchase totals =	$938.67		$1,033.5291	$1,033.54	$1,033.55	$1,033.70