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	$218.45	10.660%	$241.7368	$241.74	$241.75	$241.70
Purchase #2	$46.45	8.319%	$50.3142	$50.31	$50.30	$50.30
Purchase #3	$173.89	8.628%	$188.8932	$188.89	$188.90	$188.90
Purchase #4	$117.58	9.396%	$128.6278	$128.63	$128.65	$128.60
Purchase #5	$123.45	4.398%	$128.8793	$128.88	$128.90	$128.90
Purchase #6	$31.31	6.822%	$33.446	$33.45	$33.45	$33.40
Purchase #7	$142.25	4.521%	$148.6811	$148.68	$148.70	$148.70
7 purchase totals =	$853.38		$920.5784	$920.58	$920.65	$920.50