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	$100.54	3.767%	$104.3273	$104.33	$104.35	$104.30
Purchase #2	$103.82	3.605%	$107.5627	$107.56	$107.55	$107.60
Purchase #3	$12.54	8.369%	$13.5895	$13.59	$13.60	$13.60
Purchase #4	$183.99	3.433%	$190.3064	$190.31	$190.30	$190.30
Purchase #5	$208.75	6.351%	$222.0077	$222.01	$222.00	$222.00
Purchase #6	$61.36	10.428%	$67.7586	$67.76	$67.75	$67.80
Purchase #7	$234.93	10.572%	$259.7668	$259.77	$259.75	$259.80
7 purchase totals =	$905.93		$965.3190	$965.33	$965.30	$965.40