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	$30.80	8.377%	$33.3801	$33.38	$33.40	$33.40
Purchase #2	$12.27	13.828%	$13.9667	$13.97	$13.95	$14.00
Purchase #3	$218.42	13.698%	$248.3392	$248.34	$248.35	$248.30
Purchase #4	$109.47	3.708%	$113.5291	$113.53	$113.55	$113.50
Purchase #5	$225.85	13.593%	$256.5498	$256.55	$256.55	$256.50
Purchase #6	$108.88	6.767%	$116.2479	$116.25	$116.25	$116.20
Purchase #7	$165.89	10.661%	$183.5755	$183.58	$183.60	$183.60
7 purchase totals =	$871.58		$965.5883	$965.60	$965.65	$965.50